From migrants to proletarians : employment experience, mobility and wages in Tanzania

Prepared 5 y : J . B. K n i g h t , Oxford l i n i v e r s i t y R.H. S a b o t , 3E2PAI l n e r . ~ r l ddanK W a s h i n g t o n , DC 2 d L 3 3 5'SX  Abstract An establishment-based survey of employees in the Tanzanian nanufacturing sector yields evidence of a marked change in the stability of urban workers. Migration for wage employment was circular and short-term; today the urban wage labor force is highly stable. Using earnings function analysis, explanation for this change in behavior is sought in the structure of incentives. Particular attention is paid to the difference in returns between general and firm-specific training. The determinants of (voluntary and iilvoluntary) mobility between firms as well as between urban and rural areas are also acalyzed.  1. INTRODUCTION I t i s c h a r a c t e r i s t i c o f economic d e v e l o p m e n t t h a t t h e r e emerges a s t a b l e and c o m i i t t e d p r o l e t a r i a t p o s s e s s i n g t h e 1 s k i l l s n e e z e d by t h e e x p a n d i n g n o d e r n s e c t o r o f t h e economy. Our p u r p o s e i n t h i s p a p e r is t o d e s c r i b e a n d e x p l a i n t h e s t r u c t u r e of incentives which,fosters t h i s process, i l l u s t r a t i n g from a s u r v e y o f m a n u f a c t u r i n q employees i n T a n z a n i a , We w i s h t o d i s c o v e r w h e t h e r , how, a n d why c m ~ l o y m e n te x p e r i e n c e i s r e w a r d e d by e m p l o y e r s , a n d what are t h e c a u s e s a n d c o n s e q u e n c e s o f w o r k e r m o b i l i t y between e m p l o y e r s . The wage l a b o u r force i n T a n z a n i a h a s i n d e e d u n d e r g o n e a t r a n s i t i o n from s h o r t - t e r m m i s r a n t t o p r o l e t a r i a n s t a t u s : from i n s t a b i l i t y . honogeneity and from l a c k o f c o m i t m e n t and s k i l l s t o s t a b i l i t y , coimitment and h e t e r o g e n e i t y o f .., . skills. I n t h e c o l o n i a l past t h e wage s t r u c t u r e i n a g r i c u l t u r e , w h i c h p r o v i d e d ' m o s t wzge employment, a n d i n much o f t h e urban s e c t o r d i d n o t o f f e r incentives f o r workers t o a c c u m - l a t e employment e x p e r i e n c e . The e a r n i n g s - e x p e r i e n c e p r o f i l e was t y p i c a l l y h o r i z o n t a l . The e x p l a n a t i o n is t o b e f o o n d i n t h e u n s k i l l d d n a t u r e o f waqe employment t h e n a v a i l a b l e . N o c o s t l y t r a i . ; , L n g p e r i o d was r e q u i r e d f o r m t r y i n t o t h e - majority of j o b s , nos d i d t h e s e jobs p r o v i d e o p p o r t r l n i t i e s '3 C f o r learning-by-doi-q. F o r e n ~ l o y e r st h e b e n e f i t s o f h a v i n g * * - +I e x ? e r i c n c e d l a b o u r f o r c e were n e g l i g i b l e : c r u d e p h y s i c a l l a b o i r r was enough. 1. Accounts o f t h i s F r o c e s s o c c u r r i n g i n A f r i c a n c o u n t r i e s a r e t o be f o u n d in E l k a n (13GO) f o r Uganda a n d S a b o t (1979) f o r Tanzania.  Our e v i d e n c e w i l l show t h a t t h i s i s llot t h e case i n t h e m a n u f a c t u r i n g s e c t o r which d e v e l o p e d r a p i d l y a f t e r t h e a c h F e v e n e n t o f I n d e p e n d e n c e i n 1961. The i n c e n t i v e s f o r m a n u f a c t u r i n g w o r k e r s t o a c c u m u l a t e wage e m p l o y n e n t e x p e r i e n c e are substantial. The a e a n l e n g t h o f wage e c p l o y n e n t e x p e r i e n c e amcng A f r i c a n r e g u l a r e m p l o y e e s i s no less t h a n 9.0 y e a r s . On a v e r a g c a w o r k e r w i t h 9 y e a r s o f e x p e r i e n c e who i n o t h e r r e s p e c t s h a s t h e same c h a r a c t e r i s t i c s a s a w o r k e r w i t h o n e y e a r i s p a i d o v e r a t h i r d a s much a g a i n . Length o f employment e x p e r i e n c e i s s e c o n d o n l y t o e d u c a t i o n a l attainment a s a p r e e i c t o r of t h e earnings o f African r e g u l a r employees. Growth i n t h e r e w a r d s f o r e x p e r i e n c e i s t o b e e x p l a i n e d m a i n l y by s e c t o r a l c o m p o s i t i o n o f employment: t h e movement being from a g r i c u l t a r e t o t h e urban s e c t o r and, w i t h i n t h e u r b a n sector, t o m a n u f a c t u r i n g . T h i s h a s p r o d u c e d a con- t r a c t i o n of u n s k i l l e d l a b o u r and a n e x p a n s i o n i n t h e number o f j o b s which r e q u i r e t r a i n i n g and o f f e r s c o p e f o r l e a r n i n g by d o i n g . The c o l o n i a l s y s t e m o f s h o r t - t e r m c i r c u l a r n P l g r a t i o n between shamba and p l a n t a t i o n o r be'uean shamba a n d town h a s becoxe i n c o m p a t i b l e w i t h t h e ne:J r e q u i r e m e n t s - o f a s t a b l e , espcricncec! and r e l a b i v e l y s k i l l e d l a b o u r f o r c e . The i n c e n t i v e f o r employers t o a t Z n p t t o r e d u c e t h e t u r n - o v e r o f t h e i r w o r k e r s i s now m o r e % r e v a l e n t . h The s u b s t a n t i a l r i s e i n u r b a f i w a g e s r e l a t i v e t o r u r a l incomes was t h e p r i n c i p a l means by which t h e m i g r a n t l a b o u r s y s t e n was e r o d e d . ' H i g h e r u r b a n wages p r o v i d e d b o t h t h e 1 . S a b o t ( 1 9 7 9 ) , c h s . 7 and 8. i n c e n t i v e and t h e o p p c r t u n i t y f o r s t a b i l i z a t i o n : t h e y r a i s e d t h e o p p o r t u n i t y c o s t o f l e a v i n g u r b a n employment f o r s p e l l s o f t e n d i n g t h e f e m i l y _ s h a m b a , a n d t h e y made i t p o s s i - b l e f o r a m i g r a n t t o s u p p o r t h i s f a m i l y i n t h e town. The rise i n wages eventually g e n e r a t e d a n u r b a n l a b o u r s u p p l y i n e x c e s s o f t h e demand, s o p r o v i d i n g i n c u n b e n t s w i t h a g r e a t e r i n c e n t i v e t o h o l d o n t o wage j o b s . bloreover, t h e i n t r o d u c t i o n o f wage s t r u c t u r e s w h i c h r e w a r d e d e x p e r i e n c e i n c r e a s e d t h e o p p o r t u n i t y cost o f . l e a v i n g wage employment a n d c c n t r i b u t e d to t h e s t a b i l i z a t i o n of labour. W e are a b l e t o e x p l o r e t h e r e l a t i o n s h i p b e t w e e n employ- ment e x p e r i e n c e a n d e a r n i n g s , and t h e r e a s o n s f o r t h i s r e l a t i o n s h i p , i n ways which r e p r e s e n t a n a d v a n c e o n e x i s t i n g work. A l n o s t a l l t h e l i t e r a t u r e which e x a m i n e s t h e r e l a t i o n between s k i l l - f o r m a t i o n a n d e a r n i n g s u s e s a v a r i a b l e o f t h e f o r m (A-E-G) a s a p r o x y f o r employment e x p e r i e n c e , w h e r e A is t h e a g e of a worker and E h i s y e a r s o f e d u c a t i o n . Our s u r v e y p r o v i d e s i n f o r m a t i o n n o t o n l y o n t h e a c t u a l number o f y e a r s o f wage employment b u t a l s o o n l e n g t h o f employment i n t h e c u r r e n t j o b and i n p r e v i o u s j o b s ; and w e have i n f o r m a t i o n o n t h e e x t e n t o f 2nd m o t i v e s f o r i n t e r - f i r m m o b i l i t y of our sample. T h i s evidence e n a b l e s u s t o examine and c o a ? a r e h y p o t h e s e s a b o u t t h e s t r u c t u r e o f e a r n i n g s which : '$ - a r e drawn f r o m t h e r i v a l 'human c a p i t a l ' a n d ' i n t e r n a l a . labour market' t h e o r e t i c a l frarne~~~orks. o u r e v i d e n c e i s drawn was conducte2' The s u r v e y f r o m { ~ h i c h by S a b o t i n 1 9 7 1 . I t c o v e r e d some 1 , 0 0 0 e m p l o y e e s i n t h e m a n u f a c t u r i n g s e c t o r o f Dar e s Salaam. The s a m p l e was b a s e d o n a randcr:! r c l e c t i o n o f 47 f i r m s , s t r a t i f i e d by s i z e o f f i r m , a n d random 9r s t r a t i f i e d s a n p l i n g o f e m p l o y e e s w i t h i n each firm. D e t a i l e d i n t e r v i e w s were c o n d u c t e d w i t h e a c h o f t h e r e s p o n d e n t s , a n d employment h i s t o r i e s p i e c e d t o g e t h e r . S e c t i o n 2 of t h e paper provides a c o n v e n t i o n a l a c c o u n t o f t h e r e l a t i o n between a g g r e g a t e employment e x p e r i e n c e and earnings. By c m t r a s t , s e c t i o n 3 d i s a g g r e g a t e s employ- ment e x p e r i e n c e t o e x a m i n e t h e d i s t i n c t i o n between f i r m - s p e c i f i c a n d g e n e r a l s k i l l s ; i t a l s o c o m p a r e s human c a p i t a l with i n t e r n a l labour market i n t e r p r e t a t i o n s of t h e f i n d i n g s . S e c t i o n 4 p r e s e n t s some r e l e v a n t r e s u l t s o n t h e d e t e r m i n a t i o n o f i n t e r - f i r m m o b i l i t y , and s e c t i o n 5 c o n s i d e r s t h e e f f e c t s of l a b o u r m o b i l i t y on e a r n i n g s . Section 6 concludes. 2. A CONVENTIONAL ACCOGNT The c o n v e n t i o n z l t r e a t n e n t of employment e x p e r i e n c e i n e a r n i n g s f u n c t i o n a n a l y s i s assumes t h a t it g i v e s r i s e t o g e n e r a l s k i l l s which, i n c o m p e t i t i v e markets, p o s s e s s a market v a l u e - S i n c e such s k i l l a c q u i s i t i o n r a i s e s t h e m a r g i n a l p r o d u c t o f w o r k e r s e q u a l l y i n many employments, c o m p e t i t i o n amonq e n p l o y e r s e n s u r e s t h a t t h e wage r a t e rises ' t o maintain e q u a l i t y with t h e marginal product. The employer c a n n o t c a p t u r e any o f t h e r e t u r n on t h e c o s t s involvcd i n t r a i n i n g o r i n learning-by-doing, - and i s t h e r e - f o r e u n w i l l i n g t o pay f o r t h e s e c o s t s . of s k i l l - a c q u i s i t i o n t h e wage r e c e i v e d . Duriw t h e period is t h c a c t u a l marginal p r o d u c t minus any t r a i n i n g c o s t s . The g r a p h Of -.-?age a g a i n s t employnent e x p e r i e n c e i s l i k e l y i n i t i a l l y t o b e u p x a r d s l o p i n g : low a t f i r s t b e c a u s e t r a i n i n g c o s t s a r e d e d u c t e d from t h e wage b u t r i s i n g a s t h e p r o d u c t of t h e w o r k e r i n c r e a s e s and a s t r a i n i n g d i m i n i s h e s . I f s k i l l acquisition c e a s e s , t h e wage c u r v e r e a c h e s a p e a k , a n d i f human c a p i t a l d e p r e c i a t e s w i t h t i n e , t h e wage t h e n b e g i n s t o f a l l . Hence t h e l i k e l i h o o d o f a c o n c a v e wage-experience p r o f i l e i n t h e c a s e of g e n e r a l s k i l l a c q u i s i t i o n . The s u r v e y d a t a are c o n s i s t e n t w i t h t h e c o n v e n t i o n a l e x p l a n a t i o n of t h e r e l a t i o n between employment e x p e r i e n c e and e a r n i n g s . T a b l e 1 p r e s e n t s t h e r e s u l t s of e a r n i n g s f u n c t i o n a n a l y s i s i n which y e a r s i n wage employment [L2) is i n c l u d e d a s a c o n t i n u o u s v a r i a b l e t o r e p r e s e n t o n - t h e - j o b s k i l l acquisition. I n order t o t e s t f o r non-linearity in t h e r e l a t i o n s h i ? between e a r n i n g s and e x p e r i e n c e , t h e s q u a r e d tern !L2) o r t h e dummy v a r i a b l e s L21 (1-3.9 years of employment e x p e r i e n c e , t h e b a s e dummy) , L22 (4-7.9 years) , L23 (8-11.9 y e a r s ) a n d L24 ( 1 2 o r more y e a r s ) a r e i n t r o d u c e d . Other p e r s o n a l c h a r a c t e r i s t i c s a r e included i n t h e - e q u a t i o n s - formal t r a i n i n g , e d u c a t i o n , age, occupation, s e x and migrant status - b u t o n l y t h e e x p e r i e n c e v a r i a b l e s and t h e , f o r m a l training variable a r e reported i a the table. S i x equations - a r e p r e s e n t e d , p e r m i t t i n g 2 forms of t h e e a r n i n g s v a r i a b l e and 3 of t h e e ' g e r i e n c e v a r i a b l e . Both e a r n i n g s (N) and l o g e a r n i n g s (21 a r e t r i e d a s d e p e n d e n t v a r i a b l e s , a l t h o u g h t h e b s t r i c t hunrm c a p i t a l formulation of t h e r e l a t i o n between e a r n i n g s and e d u c a t i o n i m p l i e s t h a t t h e l o g a r i t h m i c form of t h e dependent v a r i a b l e is c o r r e c t . Employment e x p e r i e n c e i s  Table 1 Human C a p i t a l V a r i a b l e s in E a r n i n g s F u n c t i o n s f o r A f r i c a n R e g u l a r Employees Form o f e x p e r i e n c e v a r i a b l e : e L2 L2 and (L2)' L 2 dummies Mean r Form o f e a r n i n g s v a r i a b l e : W Z W Z \d Z input values I i Independent v a r i a b l e s : F' 2 74. l o * 0.141* 72. OZ* 0.135" 75.35* 0.142* 0.06 L2 13.42** 0.027** 23.11** 0.056** 9.02 (L2) -0.33* -0. OOll* I, 2 2 ~ 2 3 52.22** 0.13e* 0.33 Id24 ll6.15** 0.289** 0.19 193.44** 0.429** 0.25 constant 23.89 4.968 -15.00 4.854 56.89 5.012 R~ 0.419 0.454 0.413 0.465 0.405 0.450 F 45.94 54.76 43.08 52.80 38.72 47.91 - 10 w - r l N o t e s : The o t h e r i n d e p e n d e n t v a r i a b l e s i n c l u d e d i n t h e e q u a t i o n s b u t n o t r e p o r t e d i n t h e t a b l e a r e a g e , e d u c a t i o r o c c u p a t i o n , m i g r a n t s t a t u s , and sex dummy v a r i a b l e s . F o r t h e s a m p l e , N = 777 a n d t h e mean v a l u e s o f W a n d Z a r e 336.2 ( s h i l l i n g s p e r month) and 5.649 respcctively. 1 * i n d i c a t e s t h a t t h e c o e f f i c i e n t is signiEicant a t t h e 5 p e r c e n t l e v e l . * * i r i d i c a t e s t h a t t h e c o e f f i c i e n t is s i g n i f i c a n t a t t h e 1 p e r c e n t l e v e l .  i n c o r p o r a t e d a s L2, a s L2 and (L2) 2 , and a s t h e f o u r L2 dummy v a r i a b l e s . T h e a n a l y s i s r e l a t e s t o t h e 777 A f r i c a n r e g u l a r employees i n t h e s a m p l e . - I n t e r m s o f goodness of f i t , t h e r e i s l i t t l e t o choose between t h e W a n d t i l e Z a q u a c i o n s . Significant coefficients a r e o b t a i ~ e c lf o r a l l t h r e e f o r m s o f t h e e x p e r i e n c e v a r i a b l e , and it i s d i f f i c u l t t ? choos, t:3ng them. When L2 a l o n e i s i n c l u d e d , t h e c o e f f i c i e n t s a r e p o s i t i v e and v e r y h i g h l y s i g n f i c a n t ( t h e v a l u e s o f F rangr. f r o m 59 t o 8 2 ) . In p r o p o r t i o n a t e f o r m , t h e y i m p l y a n i n c r e a s e o f 2.7 p e r c e n t i n e a r n i n g s f o r e a c h a d d i t i o n a l y e a r o f wage employment. The i n c l u s i o n of ( L 2 I 2 a s w e l l a s L2 d o e s n o t i m p r o v e t h e p r e d i c t i v e power o f t h e e q u a t i o n s . The v a l u e o f t h e c o e E f i c i e n t o n L 2 i s r o u g h l y d o u b l e d , t o 0.55 i n t h e Z form, and it remains 2 . significant a t the 1 per cent level. The c o e f f i c i e n t o n (L2) is n e g a t i v e , a s p r e d i c t e d , and s i g n i f i c a n t l y s o . The c o e f f i c i e n t s i n t h e 1 c a s e s imply a peaking o f t h e e a r n i n g s - e x p e r i e n c e p r o f i l e a t b e t v e e n 2 4 and 30 y e a r s o f e x p e r i e n c e i n wage employment .' Thus f e w e r t h a n 2 p e r c e n t o f ' t h e s a m p l e x o u l d h a v e g o n e beyond t h e p e a k . The u s e of e x p e r i e n c e * dummy v a r i a b l e s a g a i n p r o d u c e s h i g h l y s i g n i f i c a n t p o s i t i v e c o e f f i c i e n t s (with l e s s than 4 years of experience being t h e base dunny). The c o e f f i c i e n t s r i s e c o n s i s t e n t l y u p t o and c a t e g o r y ( 1 2 o r more y e a r s including the highest e x ~ e r i e n c e of experience) . I 1 . The peak i s d r i v e d Sy d i f f e r e n t i a t i n g t h e f u n c t i o n a ( L 2 ) + b ( L 2 I 5 and s o l v i n g a + 2 b i L 2 ) = 0 .  Another r e s u l t is i n l i n e w i t h t h e c o n v e n t i o n a l e x p l a n a t i o n of t h e e x p e r i e n c e - e a r n i n g s relation. Whether o r n o t a worker has r e c e i v e d f o r m a l t r a i n i n g i s i n c l u d e d a s a dummy v a r i a b l e among t h e independent v a r i a b l e s . The co- e f f i c i e n t o a F 2 i n d i c a t e s t h e formal t r a i n i n g a d d s 1 3 per cent t o earnings. ;.!oreover, when t h e sample i s s t r a t i f i e d by l e n g t h o f employment e x ~ e r i e n c e ,w e f i n d t h a t , i n e a r n i n g s f u n c t i o n s w i t h t h e d e p e n d e n t v a r i a b l e i n l o g a r i t h m i c form, t h e c o e f f i c i e n t on f o r m a l t r a i n i n g L s i n i t i a l l y n e g a t i v e and s u b s e q u e n t l y p o s i t i v e and r i s i n g w i t h l e n g t h of e x p e r i e n c e : y e a r s o f employment e x p e r i e n c e : 0-3.9 4-7.9 8-11.9 12- c o e f f i c i e n t o n F2 : -0.127 0.051 0.193 0.311** T h i s i s what human c a p i t a l t h e o r y would p r e d i c t . The employee h a s t o pay, i n t h e form of a lower wage, f o r t r a i n i n g i n m a r k e t a b l e s k i l l s , and s u b s e q u e n t l y d e r i v e s a r e t u r n from t h e investment . Our r e s u l t s a r e c l e a r l y c o n s i s t e n t w i t h t h e human c a p i t a l t h e o r y o f t h e r e l a t i o n between e x p e r i e n c e and e a r n i n g s . ohe ever, i t i s one t h i n g t o f i n d e v i d e n c e which i s c o n s i s t e n t -. with t h e t h e o r y ; i t i s a n o t h e r t o t e s t t h e human c a p i t a l h y p o t h e s i s a g a i n s t competing h y p o t h e s e s which a r e a l s o c o n s i s t e n t with t h e evidence. We m u s t guard a g a i n s t t h e warning t h a t ' i n s t e a d o f a t t e m p t i n g t o r e f n A e t e s t a b l e - p r e d i c t i o n s , economists spend much of t h e i r t i n e show in* t h a t t h e r e a l world b e a r s o u t t h e i r ~ r e d i c t i o n s ,t h u s r e p l a c i n g f a l s i f i c a t i o n which is d i f f i c u l t , w i t h c o n f i r m a t i o n , which ** i n d i c a t e s t h a t t h e c o e f f i c i e n t is s i g n i f i c a n t a t t h e 1 per cent level. is easy'.' I n t h e n e x t s e c t i o n we show t h a t d i s a g g r e g a t i o n of t h e employment e x p e r i e n c e v a r i a b l e c a n p r o d u c e e q u a l l y s i g n i f i c a n t r e s u l t s , and t h a t t h e s e a r e amenable t o more than one i n t e r p r e t a t i o n . , 3 . FIF3.1-SPECIFIC SKILLS: XlD 1NTERN.X LABOUR I-IARKETS F i r m - s p e c i f i c s k i l l s d i f f e r from g e n e r a l s k i l l s i n t h a t t h e y p c s s e s s no m a r k e t v a l u e : t h e wage which a n employee c a n o b t a i n i n o t h e r f i r m s is independent of t h e s k i l l s h e h a s acquired i n h i s c u r r e n t firm. If t h e wage p a i d i n h i s c u r r e n t job is t h e r e f o r e a l s o independent of h i s s k i l l s , t h e f i r m derives a l l t h e b e n e f i t of h i s skill-acquisition and t h e employee d e r i v e s noce. T h i s would imply t h a t t h e f i r m b o t h e n j o y s t h e b e n e f i t s and p a y s t h e c o s t s o f s p e c i f i c t r a i n i n g . In long run e.pilibrium, when t h e d i s c o u n t e d f l o w s o f b e n e f i t s a n d costs a r e e q u a t e d , t h e wage d u r i n g t h e p e r i o d of t r a i n i n g i s e q u a l t o t h e p o t e n t i a l m a r g i n a l p r o d u c t , i.e. the actual marginal product p l u s t h e opportunity c o s t of t i m e s p e n t i n training. The wage-experience p r o f i l e s h o u l d b e h o r i z o n t a l . 1. Blaug i n L a t s i s ( 1 9 7 6 ) .  T h i s ary7:r.ent i g n o r e s t h e p o s s i b i l i t y o f l a b o r t u r n o v e r , which i n v o l v s s a t r a i n i n g c o s t . The employee, b e i n g a f f e c t a d n e i t h e r by t h e c o s t n o r by t h e b e n e f i t o f s p e c i f i c t r a i n i n g , is i n d i f f e r e n t between remain.ing i n h i s p r e s e n t employment a n d q u i t t i n g t o t a k e a n o t h e r job. The firm, however, is n o t ' I i n d i f f e r e n t t o such turnover: t h e replacement of l a b o r involves . an additional t r a i n i n g cost. Labor t u r n o v e r i s a d e c r e a s i n g f u n c t i c n o f t h e wage. The employer t h e r e f o r e h a s an i n c e n t i v e t o p a s s on t h z b e n e f i t s of s p e c i f i c s k i l l a c q u i s i t i o n t o t h e employee i n returr! f o r tile sale o f t r a i n i n g . Indeed, t h e , employer c a n a v o i d t u r n o v e r c o s t c o m p l e t e l y by p a s s i n g o n t h e f u l l b e n e f i t f r o n speciEic t r a i n i n g t o t h e c n p l o y 9 e a n d extra-:- ting t h e f u l l cost o f t r a i n i n g from h5m. I t is t h e n t h e employee who b z a r s t h e r i s k : t h e r i s k o f b e i n g f i r e d b e f o r e h i s chosen p e r i o d of employment h a s e l a p s e d . The e f f e c t of r i s k b e a r i n g Sy the employee i s t o i n c r r - s e t h e wage n e e s e d t o r . e n s u r e t h a t h i s r e q u i r e d r a t e of r e t u r n i s s e c u r e d , and t h u s  t o r a i s e t h e c o s t t o t h e employer. An arrangement i n which t h e c o s t s and b e n e f i t s a r e s h a r e d , s o g i v i n g both p a r t i e s a n i n c e n t i v e t o reduce t u r n o v e r may t h u s ,e t h e most p r o f i t a b l e , - Iri ;i low-income c o u n t r y l i k e Tanzania t r a i n i n g c o s t s may exceed both t h e wages and t h e f i n a n c i a l r e s o u r c e s o f potential trainees. C a p i t a l market i n p e r f e c t i o n s and t h e l i m i t e d scope f o r d e p r e s s i n g t h e i r wages d u r i n g t h e t r a i n i n g . p e r i o d may t h u s p r e v e n t employees from f i n a n c i n g t h e i r t r a i n - - -. . ing. :" 1f h e h a s ' t o bear t h e t r a i n i n g c o s t s , t h e employer h a s an i n c e n t i v e t o r a i s e t h e wage paid t o workers w i t h firm- . . s p e c i f i c s k i l l s by an amount depending on t h e c o s t o f t u r n o v e r and t h e response of t u r n o v e r t o wage i n c r e a s e s . he e q u i l i - brium c o n d i t i o n f o r wage determination i s t h a t t h e c o s t o f ii marginal wags i n c r e a s e s h o c l d equal t h e cc..sequent de:. r e a s e t r a i n i n g cost. That i s t h e form i n which t h e ' l a b o r t u r n - o v e r ' model of wage d e t e r m i n a t i o n i s normally c a s t . ' The t h e o r e t i c a l a n a l y s i s i n d i c a t e s t h a t e a r n i n g s c a n be expected t o i n c r e a s e w i t h employment e x p e r i e n c e w h i l e s k i l l s c o n t i n u e t o be a c q u i r e d , whether t h e s e s k i l l s a r e of a f i r m - * s p e c i f i c o r of a g e n e r a l n a t u r e . In perfectly competitive mark=ts t h e payment i s e q u a l t o t h e marginal p r o d a c t of - t r a i n i n g ' n t h e c a s e of g e n e r a l s k i l l s and b e a r s a p o s i t i v e S t i g l i t z ( 1 9 7 4 ) . I f t h e sk i l l s a r e g e n e r a l t h e a n a l y s i s .. does n o t a a b l v because 4 - - - the e -n~lov & - - * -e- ecan e x t r a c t --- a1 1 t b e n e f i t o f t r a i n i n g . T h i s i s - t h e c a s e i n which t h e r e s u l - -..- he t a n t s o c i a l s u b - o p t i s a l i t v o f d n v e s t r n e n t i n t r a i n i n a would a ---- j u s t i f y governxien= i n t e r v e n ti& i n t h e form of f u n d s o r subsidies for training.  Table 2 The Coefficients on Years i n C u r r e n t and i n Previous Employment, African Regular Employees :. Form of experience v a r i a b l e : No squared terms '. Squared tcrms . Mean ,: ' Form of e a r n i n s s v a r i a b l e : w 2 W 2 input : .'l 1 I Cocff i c i c n t s o f : S.E.E. F Notes: O t h e r independent v a r i a b l e s Included i n t h e r e g r e s s i o n e q u a t i o n b u t n o t r e p o r t e d i n the t a b l e a r e : E , and t h e age, occupation, migrant s t a t u ? , s e x , and formal t r a i n i n g durmy v a r i a b l e s . The mean v a l u e s of !-I and Z a r e 336.15 and 5 . 6 4 9 r e s p e c t i v e l y ; t h e v a l u c of N i s 777. * i n d i c a t e s t h a t t h e cocfficient'is s i g n i f i c a n t a t t h e 5 per c e n t l e v e l . ** i n d i c a t e s t h a t t h e c o e f f i c i e n t i s s i g n i f i c a n t a t t h e 4 per c e n t l e v e l . '. -- .. & i.n s t a n c e , --- -.--. z o z p e t i t i v e l a b o u r . marlei-s a s expounded, t ..I-- _ -' by c a r y a r c k e r . ' However. - _. is n o t necessarily the case t h a t the e f f e c t s of s k i l l acquisition on e a r n i n g s a r e deterztined by market f o r c e s . I c t e r n a l labor m a r k e t s may be s e e n as t h e eraployers' i n s t i t u t i o n a l r e s p o n s e t o t h e p r o b l m s o f ' r e t a i n i n g t h e b e n e f i t s of f i r m - s p e c i f i c training.' I n t e r n a l l a b o r markets p o s s e s s v a r i o u s c h a r a c t e r i s - t i c s which nay s e r v e t h i s f u n c t i o n . I n t h e o r y t h e way t o , ... . r e t a i n - l a b o r i n which s p e c i f i c t r a i n i n g h a s been i n v e s t e d i s by means of l o n g t e r n c o n t r a c t s , b u t t h e s e a r e g e n e r a l l y .. . impracticable. However, p r o m o t i o n e l l a d d e r s and s e n i o r i t y , . r u l e s c a n h a v e t h e sme e f f e c t o f r e d u c i n g l a b o r t u r n o v e r , They a l s o h e l p t o s e c u r e employees' c o - o p e r a t i o n a t work and i n imparting s k i l l s . I n t e r n a l promotion a l s o p r o v i d e s a . s c r e e n i n g mechanism f o r s e l e c t i n g workers w i t h d e s i r a b l e c h a r a c t e r i s t i c s , and t h u s overcoming t h e problem o f i m p e r f e c t inforzation. Thus i n t e r n a l l a b o r m a r k e t s g i v e a l l employees some p r o n o t i o n b u t a l l o w f o r uneven promotion a c c o r d i n g t o a b i l i t y r e v e a l e d on t h e job. Both by r e d u c i n g l a b o r t u r n - o v e r 2nd improving i n f o r m a t i o n on i n d i v f d u a l w o r k e r s , i n t e r n a l l a b o r m a r k e t s r e d u c e t h e c o s t of s p e c i f i c t r a i n i n g t o t h e b employer. A t h e o r e t i c a l j u s t i f i c a t i o n c a n t h u s be found f o r t h e r i s i n g s e n i o r i t y scalrs which a r e c h a r a c t e r i s t i c o f i + e r n z l r - rC labor-narkets. I n s t e a d o f paying a h i g h b u t c o n s t a n t wage, * - a n o l ' 5 r way f o r a f i r m t o r e d u c e l a b o r t u r n o v e r a f t e r * n v e s t i n g i n f i r m - s p e c i f i c t r a i a i n g v~ouldbe t o pay on a r i s i n g s e n i o r i t y 1 . l i i l l i a n s o n , ldachter a n d ~ a r r x s( 1 9 7 5 ) . 2. Becker (1964). c h . 2 . scnle. P r o v i d e d t h a t t h e i n i t i a l wage i s low enough, t h e t o t a l d i s c o u n t c d c o s t t o t h e f i r m o f p a y i n g on a s e n i o r i t y s c a l e n e e d 5e no g r e a t e r t h a n t h a t f o r a c o n s t a n t wage. Given e q u a l d i s c o u n t s d c u r r e n t v a l u e s , a worker i s i n d i f f e r e n t b e t w e e n t h e two scales a t t h e t i m e o f r e c r u i t m e n t b u t t h e r e a f t e r h e p r e f e r s t h c s e n i o r i t y scale. The s h a p e b f t h e s e n i o r i t y s c a l e d e p e n d s on t t i o c o n s i d e r a t i o n s . The einployer h a s a n i n c e n t i v e t o pay a s much o f t h e wage as p o s s i b l e as l a t e as p o s s i b l e i n o r d e r t o discourage turnover. However, t h e employee, b e i n g l i m i t e d i n a c c e s s t o c r e d i t , i n knowledge o f t h e f u t u r e , and i n p r o t e c t i o n a g a i n s t f i r i n g , r e q u i r e s c o m p e n s a t i o n f o r t h e postponement o f wage p a y n e n t s . A b a l a n c i n g o f t h e s e two c o n s i d e r a t i o n s i s r e q u i r e d . I t is q u i t e p o s s i S l e f o r t h e wage s c a l e c h o s e n by t h e employer t o b e upward s l o p i n ; f o r many y e a r s a f t e r t h e t r a i n i n g h a s b e e n completed. While t h ~ e s~planationof s e n i o r i t y s c a l e s is r o o t e d i n p r o f i t - m a x i a i s i n g b e h a v i o r , t h e l i n k b e t w e e n wage and m a r g i n a l p r o d u c t i n any d r o s s - s e c t i o n s u r v e y i s c l e a r l y broken. The p i c t u r e we h a v e p a i n t e d is o n e o f i n t e r n a l l a b o r markets designed t o s e r v e t h e i n t e r e s t s of employers%nd raise profits. However, where w o r k e r s a r e c o l l e c t i v e l y well o r g a n i s e d , t h e i n t e r n a l l a b o r n z r k e t may r e f l e c t t h e b a l a n c e o f i n t e r e s t s and p o v e r between employer and w o r k e r s , w i t h P . s e c u r i t y , promotion w o r k e r s p o s s i b l y p l ~ c i n ge a p h a s i s o n ~ j o b a c c o r d i n g t o s t r i c t s e n i o r i t y , and n o t i o n s o f ' f a i r n e s s ' i n wage s t r u c t u r e . D o e r i n g e r and P i o r e , f o r i n s t a n c e , g i v e a n i n t e r p r e t a t i o n o f i n t e r n a l l a b o u r m a r k e t s which i s b r o a d e r  1 t h a n t h e s t r i c t l y economic one. The u p s h o t o f t h e a n a l y s i s is t h a t e a r n i n g s i n a n i n t e r n a l l a b o r m a r k e t a r e l i k e l y t o r i s e w i t h t h e d u r a t i o n o f employ- ment i n t h e f i r m . T h i s may w e l l r e f l e c t t h e f i r m ' s d e s i r e t o r e t a i n w o r k e r s i n whox it h a s i n v e s t e d f i r m - s p e c i f i c skills. I n t h a t case t h e i n c r e a s e i n e a r n i n g s w i t h e x p e r i e n c e i s l i k e l y t o b e a r some l o n g r u n r e l a t i o n s h i p t o t h e e m p l o y e r ' s valuation of t h e s k i l l s acquired, but t h e r e l a t i o n s h i p a t . a n y p o i n t i n t i m e may b e t e n u o u s . Moreover, t h e r e w a r d f o r s e n i o r i t y may c o n t a i n a s t r o n g c u s t o m a r y e l e n e n t a n d , i t may ' . r e f l e c t t h e employees' e x p r e s s i o n o f t h e i r c o l l e c t i v e i n t e r e s t s . ' Disaggregation of t h e earnings functions can assist i n a s s e s s i n g t h e r i v a l e x p l a n a t i o n s of t h e r e l a t i o n s h i p s between e a r n i n g s and e x p e r i e n c e . D i s a g g r e g a t i n g f i r s t by l e n g t h o f c u r r e n t Binploynent 2nd t h e n by l e n g t h o f p r e v i o u s employmen? a l l o w s u s t o examine t h e i n t e r a c t i o n s between t h e s e t w o c a t e g o r i e s of e x p e r i e n c e i n t h e i r e f f e c t s on e a r n i n g s . Table 3 presents the results. The r e t u r n s t o p r e ; i o u s employment e x p e r i e n c e d e c l i n e a s i t grows more d i s t a n t , s l o i v l y at f i r s t . , b u t t h e n r a p i d l y t o b e c o x e i n s i g n i f i c a n t beyond 8 y e a r s . ,By I c o n t r a s t , t h e r e t u r n s p e r y e a r of expe>ience i n c u r r e n t employment a r e i n s e n s i t i v e t o t h e lengthening of previous - - employment e x ? e r i e n c e , and r e m a i n s i g n i f i c a n t l y p o s i t i v e . - 5 Human c a p i t a l t h e o r y s u g g e s t s i n t e r p r e t a t i o n s o f t h e s e hresults. f i r m w i l l r e w a r d p r e v i o u s employment e x p e r i e n c e I A insofar as i t confers general skills. T h i s r e w a r d w i l l be . B 1. D o e r i n g e r and P i o r e (1971) .  .. .. -. -. ' . . a t e n t r y p o i n t s t o e d u c a t i o n , and t h e r e a f t e r t o l e n g t h o f ' employment i n t h e p u b l i c s e r v i c e s . The i n c r e a s e i n e a r n i n g s w i t h l e n g t h of p r - S l i c s e r v i c e employment may be a p o o r i c d i - c a t o r o f t h e v a l u e o f s k i l l a c q u i s i t i o n on t h e job. T h e r e is c o m p e t i t i o n between t h e m a n u f a c t u r i n g s e c t o r and p u b l i c s e r v i c e s f o r v a r i 3 u s t y p e s of l a b o r . - g. Althou h : an abundance of l a b o r r u l e s o u t such c c n p e t i t i o n a t t h e l o w e s t s k i l l l e v e l s , m a n u f a c t u r i n g f i r n s may n o t b e a b l e t o : a t t r a c t 'and r e t a i n t h e b e s t q u a l i t y workers i n s h o r t s u p p l y i f t h e y pay less t h a n t h e c o r r e s p o n d i n g p u b l i c s e r v i c e wage . . ( w i t h a d j u s t m e n t f o r non-pecuniary d i f f e r e n c e s ) . The c o e f f i c i o f e n p l o p e n t e x p e r i s n c e i n t h e p u b l i c s e r v i c e s may t h e r e f o r e s e t a lower l i n i t t o t h e c o e f f i c i e n t o f L2 f o r o u r s a x p l e . Howsver, t h e i n f l u e n c e o f t h e p u b l i c s e r v i c e s i s l i m i t e d f o r two r e a s o n s . F i r s t , t h e l o v e r l i m i t need n o t be o p e r a t i v e : . t h e c o e f f i c i e n t of e x g e r i e n c s c a n be g r e a t e r i n t h e p r i v a t e sector. Secondly, i t might be avoided. Assume t h a t a f i r n does n o t value general skill-acquisition a s highly a s implied by t h e wage-experience p r o f i l e on t h e p u b l i c s e r v i c e s . The r a t i o n a l r e s p o n s e is t o c o n c e n t r a t e on t h e employment o f p e r s o n s w i t h o u t emplc}ment e s p e r i e n c e . But i f s u b s t i t u t i o n U is n o t complete, t h e p u b l i c s e r v i c e s continue t o i n f l u e n c e m a n u f a c t u r i n g wage p r o f i l e s : f i r n s s u b s t i t u t e away f r o m long- e x p e r i e c c e wozkers u p t o t h e p o i n t a t which t h e i r n a r g i n a l p r o d u c t r i s e s t o e q u a l t h e p u b l i c s e r v i c e wage. In t h e case E of m a n u f a c t u r i n g workers who c a p w t e n t e r t h e p u b l i c s e r v i c e except a t 101.1 e n t r y p o i n t s , t h e p u b l i c s e r v i c e wzge becones l e s s r e l e v a n t a s t h e s e workers become ' l o c k ~ di n f w i t h t h e p a s s z g e o f time.  Table 5 S e l e c t e d Pav S c a l e s i n P a r a s t a t a l s , 1968 L S t a r t i n g pay Annual i n c r e 3 e n t s C e i l i n g pay (sh. p.a.) Nv~mber Size (sh. p-a.) ( s h . P-a..) . Foreman 8,880 13 480 15,120 Clerk gradei.l Clerk grade 2 2,800 1 20 3,840 1 80 4,920 Artisan grade 1 5,400 8 360 8,280 Artisan grade 2 3,840 6 180 . 4,920 Subordinate staf: 2,160 14 1 20 3,840 d i r e c t i v e implied a lozg scale f o r u.?s;rilled workers. The reason f o r t h e i n t r o d u c t i o n o f i n c r e m e n t a l s c a l e s e v e n f o r m a a u a l o c c u p a t i o n s is u n c l e a r : i t may s i m p l y h a v e b e e n a n a t t e m p t t o e x t e n d c i v i l s e r v i c e pay a r r a n g e m e n t s i n . the interestsof parity. However, i t h a d t h e e f f e c t o f f a c i l i - t a t i n g t h e a c c e p t a n c e o f wage r e s t t a i n t - individuals could< l o o k f o r w a r d to pay i n c r e m e n t s - and i t was u s e d t o i n ' l u e n c e worker b e h a v i o r . ' $n..,ividuzls were d e n i e d t h e i r increr;l.e:lts 'r L - f o r u n s a t i s f a c t o r y work p e r f o r n a n c e , e f f i c i e n c y b a r s were * o p e r a t e z , a n d c ? o u b l p i n c r e n e r l t s were g i v e n t o v e r y d i l i g e n t I workers. I n o t h e r words, t h e pzy s t r u c t u r e impost-d o n t h e p a r a s t a t a l s was t o s o n e e x t e n t u s e d - i n accordaxe with intern21 1. Jackson (197 9), pp. 49-52.  l a b o r market t h e o r y - t o p r o v i d e incen. t i v e s f o r h i g h p t i v i t y and skj.11 a c q u i s i t i o n . The e x i s t e n c e of f o r m a l i n c r e - m e n t a l s c a l e s i n p a r a s t a t a l s does n o t p r o v i d e a f u l l e x p l a n a - t i o n of our r e s u l t s , f o r t h r e e reasons. Plany p a r a s t s t a l employees may s t i l l have been above t h e s c a l e s i n 1 3 7 0 . P a r a s t a t a l s accounted f o r on1.y a m i n o r i t y of err.ployees.in t h e 24 l a r g e f i r m s ( 4 3 p e r c e n t ) , and no doubt £ o r a much s m a l l e r p r o p o r t i o n i n the sample a s a whole. Finally, t h e f a c t of f o r m a l i n c r e m e n t a l s c a l e s l e a v e s &en t h e q u e s t i o n o f t h e i r ! rationale.  relationships. F o r t h e sample a s a whole, w e f i n d t h e f o l l o w i n g r a t e s of m o b i l i t y : M VM IM *. Mean v a l u e 0.137 0.081 0.056 - . Var i a n c e 0.032 0.020 . . . . :. , . , . .. . ...:-. .. ... ..... . .. . . . . . . . . . .. .& , T h e . a v e r a g e number o f j o b changes p e r y e a r o f wage employ- .... . .. -. -. . .... , m e n t w a s 0.137, i. e. . a change o f j o b o c c u r r e d on a v e r a g e o n c e . . e v e r y 7.3 y e a r s , a n d a v o l u n t a r y change o n l y e v e r y 1 2 . 3 y e a r s . A s expected, t h i s i n d i c a t e s a manufacturing l a b o r f o r c e which h a s been v e r y immobile b e t v e e n employers. Voluntary moves o u t n u n b e r e d i n v o l u n t a r y o n e s ; the two r a t e s combined of c o u r s e sum t o t h e r ; t e of t o t a l mobility. . F u r t h e r e v i d e n c e o f t h e l a c k of m o b i l i t y among nanu- f a c t u r i n g workers is p r o v i d e d by t h e f o l l o w i n g s t a t i s t i c s : mean median standard deviation Y e a r s i n wage employment 8.8 7.1 6.0 I Y e a r s i n c u r r e n t employment 4.1 3.8 2.4 Number o f j o b s h e l d 2.2 1.9 1.1 e 2 The d i s t r i b u t i o n o f t h e s a n p l e a c c o r d i n g t o t h e number of j o b s h e l d ( i n c l u d i n g t h e c u r r e n t one) i s a s f o l l o i i s : Number o f jobs: 1 2 . - 4- 3 Percentage: 36 34 18 ' :1 2 T h e s e f i g u r e s c o n f i r n t h e f a c t t h a t we a r e d e a l i n g w i t h a s t a b l e g r o u p and t h a t many m a n u f a c t u r i n g employees a r e keen t o h o l d on t o t h e i r j o b s i n t h e face of s t i f f c o m p e t i t i o n .  . Table 6 - - The Coefficients of the Independent Variables in obil lit^ Functions . .: Specification: OLS additive Poisson multiplicative 1 Dependent variable: M IM'. . VM PlOB 1 MOB 2 MOB 3 I . Value of coefficient: 1 ( t a b l e continued) very l i t t l e - less than 5 per c e n t - of the variation in mobility can be explained. Sone o f t h e i n d e p e n d e n t v a r i a b l e s would n e v e r t h e l e s s p a s s t h e u s u a l s i g n i f i c a n c e t e s t s . The P o i s s o n d i s t r i b u t i o n o f t h e d e ~ e n d e n tv a r i a b l e is no d o u b t m a i n l y r e s p o n s i b l e f o r t h e low v a l u e s of R -2 . The r e g r e s s i o n a n a l y s F s i n d i c a t e s t h a t employment experience diminishes mobility: t h e c o e f f i c i e n t on L 2 i s n e g a t i v e i n t h e c a s e of both IM and V M and s i g n i f i c a n t l y s o f o r t h e former. The c o r r e s p o n d i n g acd e q u i v a l e n t r e s u l t i n t h e c a s e o f NOB 2 and MOB 3 i s t h a t t h e c o e f f i c i e n t on L2 is l e s s t h a n u n i t y and s i g n i f i c a n t l y s o f o r t h e f o r m e r , i . e . sm r~~~xperienc r k e r s a r e more l i k e l y t o l o s e t h e i r j o b s t h a n ed a r e experienced workers. The d e c l i n e i n v o l u n t a r y m o b i l i t y a s employment e x p e r i e n c e l e n q t h e n s may r e f l e c t t h e t r i a l - a n d - e r r o r p r o c e s s by which e n t r a n t s t o t h e l a b o r f o r c e g r a d u a l l y a c q u i r e i n f o r m a t i o n a b o u t t h e m s e l v e s and a b o u t j o b s . The d e c l i n e i n i n v o l u n t a r y m o b i l i t y may b e a n i n d i c a t i o n t h a t u n s a t i s f a c t o r y w o r k e r s a r e weeded o u t o f t h e m a n u f a c t u r i n g s e c t o r , o r t h a t t h e more e x p e r i e n c e d w o r k e r s a r e more v a l u a b l e I t o employers. The c o e f f i c i e n t of r e g u l a r e m p l o p e n t s t a t u s i s s i ~ z n i f - - i c a n t l y n e g a t i e i n the case of involun^_tarymcbility. The i C h i g h r a t e o f i n v o l u n t a r y n o b i l i t y among t h o s e c u r r e n t l y * c a s u a l employmgbt r e f l e c t s t h e f a c t s t h a t t h e y a r e n o t c o v e r e d v by t h e l e g i s l a t i o n p r o v i d i n g e n p l o y e s s w i t h some s e c u r i t y o f employment, and t h a c t h e demand f o r t h e i r s e r v i c e s i s concen- t r a t e d i n e n t e r p r i s e s whose o u t p u t f l u c t u a t e s s e a s o n a l l f -  I t is p o s s i b l e t h a t m i g r a n t s ( t h e t w o - t h i r d s o f t h e sample who a r r i v e d i n Dar-es-Sa1aa.n a t t h e a g e o f 14 o r o v e r ) w i l l have a h i g h e r r a t e o f v o l u n t a r y m o b i l i t y t h a n non- migrants a s a r e s u l t of return v i s F t s t o t h e r u r a l areas. Moreover, i f m i g r a n t s have p o o r e r i n f o r s a t i o n a b o u t o r a c c e s s t o j o b s t h a n urban-born p e o p l e , t 3 i S t o o w i l l r a i s e t h e i r r e l a t i v e voluntary n o b i l i t y a s w i t 5 experience they g a i n xore information o r b e t t e r contracts. The d u m y v a r i a b l e i n d i c a t i n m i g r a n t s t a t u s (N1) h a s a p o s i t i v e b u t i n s i g n i f i c a n t c o e f f i c i e n i n t h e case of voluntary mobility. In mobility functions s t r a t i f i e d by e d u c a t i o n t h e r e i s some t e n d e n c y f o r t h e m i g r a n t dummy c o e f f i c i e n t t o b e p o s i t i v e a t low l e v e l s o f e d u c a t i o n and n e g a t i v e a t h i q h l e v e l s , b u t none of t h e c o e f f i c i e n t s i s siqnificant: Years o f e d u c a t i o n : 0 1- 4 5-8 9- C o e f f i c i e n t o n PI1: 0.0152 .0224 -.0144 -.0252 T h i s r e s u l t m i g h t r e f l e c t methods o f r e c r u i t m e n t : rec t o jobs requiring education tends t o be on t h e b a s i s of a d v e r t i s e m e n t and p e r s o n a l q u a l i f i c a t i o n s w h e r e a s p e r s o n a l P i Y c o n t a c t s a r e more i m p o r t a n t i n r e c r u i t m e n t t o o t h e r j o b s . Evidence o f t h i s p a t t e r n can be found i n t h e s u r v e y . The - p r o p o r t i o n of workers applying f o r t h e i r c u r r e g t jobs s r e l a t i v e is seer! t o f a l l , and t h e p r o p o r t i o n a g p l y i n g by I - * l e t t e r t o rise, with education: @ ! I Years o f e d u c a t i o n : O: 1- 4 5-8 9- 1 Application: through relative by l e t t e r 32 0 27 6 22 18 57 I1  The i n t e r m i t t e n t c h a r a c t e r o f f e n a l e p a r t i c i p a t i o n i n t h e labo; m a r k e t s u g g e s t s t h a t t h e v o l u n t a r y n o b i l i t y of women w i l l e x c e e d t h a t o f r.en. t~owever, t h e r e g r e s s i o n s r e v e a l t h e c o e f f i c i e n t on t h e du!my v a r i a b l e m a l e s e x ( S l ) t o be p o s i t i v e , i n t h e c a s e of involuntary m o b i l i t y sicjnif- i c a n t l y so. R e g r e s s i o n s s t a n d a r d i s e d by o c c u p a t i o n sh~;.r t h e c o t f f i c i e n t s cn S1 t o be significantly negative f o r white c o l l a r employees and s i g n i f i c a n t l y p o s i t i v e f o r u n s k i l l e d employees: C o e f f i c i e n t o n S1: M VM IM White c o l l a r -0.1817** -0.li05** -0.0712** Unskilled H i g h t u r n o v e r among f e m a l e c l e r k s a n d t y p i s t s i s ~ u k w e i ~ h k c ? b y t h e p r e p o n d e r a n t g r o u p o f u n s k i l l e d wornen,who s t a y i n their jobs. T h i s s t a b i l i t y may r e f l e c t t h e i r w e a k e r c h a n c e s o f s e c u r i n g m a n u f a c t u r i n g employment i n t h e f a c e of male c o n p e t i t The r e g r e s s i o n s r e v e a l t h a t w h i t e c o l l a r s t a t u s (01 a n d 0 2 ) r a i s e s V>l a n d l o w e r s IN, w h e r 2 a s s k i l l e d l a b o r status (03) l o w e r s b o t h , i n re1atir.r t o u n s k i l l e d l z b o r ( 0 5 , t h e b a s e dummy). IIowever, t k k o c c u p a t i o n a l c o e f f i c i e n t s a r e g e n e r a l l y n o t s i g n i f i c a n t l y d i f f e r e n t from z e r o . Voluntary m o b i l i t y was h i g h e s t f o r w h i t e c o l l a r j o b s , i n w h i c h s h o r t a g e - . and * * i n d i c a t e t h a t t h e c o e f f i c i e n t i s s i g n i f i c a n t a t t h e 5 p e r c e n t and 1 p e r c e n t l e v e l s r e s p e c t i v e l y .  was g r e a t e s t , and lowest f o r s e m i - s k i l l e d j o b s (04), i n which s p e c i f i c s k i l l s were l i k e l y t o be i n p o r t a n t and g e n e r a l s k i l l s unimportant. I n v o l u n t a r y m o b i l i t y , on t h e o t h e r hand, was lowest i n white c o l l a j o b s and, w i t h i n t h e inanual c a t e g o r y , f e l l a s s k i l l l e v e l rose. Although s e m i - s k i l l e d j o b s may have t h e h i g h e s t r a t i o of f i r m - s p e c i f i c t o g e n e r a l s k i l l s , b o t h s k i l l e d and w h i t e c o l l a r jobs a r e l i k e l y t o i n v o l v e employers i n higher t r a i n i n g c o s t s . Differences i n t r a i n i n g c o s t s borne by t h e employer may w e l l e x p l a i n t h e o c c u p a t i o n a l d i f f e r e n c e s i n involuntary mobility. Our r e s u l t s , a l t h o u g h n o t s t a t i s t i c a l l ! s i g n i f i c a n t , a r e t h u s i n accordance w i t h e x p e c t a t i o n s . But even'the occu2ations with the highest r a t e s o f voluntary m o b i l i t y ( c l e r i c a l ( 0 2 ) ) and i n v o l u n t a r y m o b i l i t y ( u n s k i l l e d ) i n p l y a v o l a r ~ t a r ymcve o n l y every 8 . 2 y e a r s and a n i n v o l u n t a r y move o..ly e v e r y 14.5 y e a r s r e s p e c t i v e l y . A s t h e possession of educational q u a l i f i c a t i o n s p r o v i d e s a worker w i t h g r e a t e r m a r k e t a b i l i t y , we would e x p e c t v o l u n t a r y mobility t o i n c r e a s e w i t h y e a r s of e d u c a t i o n . Similarly, t h e s h o r t a g e o f educated workers should r e d u c e t h e i r i n v o l u n t a r y mobili'tv. The c o e f f i c i e : i t on E i s indeed s i s n i f i c a n t l v ~ o s i t i v i n t h e c a s e of v o l u n t a i y m o b i l i t y , r e f l e c t i n g t h e s t r e n g t h o f - - c o m p e t i t i o n f o r educated nanpower. When t h e c o n t i n u o u s v a r i z b l e i s ~ e p l a c e dby a s e t of e d u c a t i o n a l duJx-ny v a r i a b l e s ( w i t h E l , no e d u c a t i o n , a s t h e b a s e dummy), a s i n t h e P o i s s o n n u l t i p l i c - a t i v e r e g r e s s i o n s , i t i s c l e a r t h a t t h e c o e f f i c i e n t of primary educati2,l (E4) is l a r g e l y r e s p o n s i b l e . REFERENCES B e c k e r , Gary S. Human C a p i t a l . -4 T h e o r e t i c a l a n d E m p i r i c a l Analysis with Special Reference t o Education. Princeton University Press, Princeton, 1964. 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