ECONOMIC GROWTH CENTER
                                
                        YALE UNIVERSITY
                                
                                
                        P.O. Box 208269
               New Haven, Connecticut 06520-8269
                                
                                
                                
                CENTER DISCUSSION PAPER NO. 798
                                
                                
                                
             THE EFFECTS OF AGRICULTURAL EXTENSION
                    ON FARM YIELDS IN KENYA
                                
                                
                                
                                
                       Robert E. Evenson
                        Yale University
                                
                              and
                                
                         Germano Mwabu
                     University of Nairobi
                                
                         September 1998

                         

Note: Center Discussion Papers are preliminary materials circulated to stimulate discussions and
      critical comments.

      A substantially revised version of a paper originally presented at the 10th Anniversary
      Conference on Investment, Growth and Risk in Africa at the Centre for the Study of African
      Economies, University of Oxford, Oxford, UK,  April 17-18, 1997. We received helpful
      comments from John Knight, T. Paul Schultz  and Peter Kimuyu and two anonymous
      referees.  Any remaining errors are our own.

                            ABSTRACT

The paper examines  effects of agricultural extension on crop yields in Kenya controlling for other
determinants of yields, notably the schooling of farmers and agro-ecological characteristics of arable
land.  The data we use were collected by the Government of Kenya in 1982 and 1990, but the
estimation results reported in the paper are based primarily on the 1982 data set. The sample used
for estimation contains information about crop production, agricultural extension workers
(exogenously supplied to farms), educational attainment of farmers, usage of farm inputs, among
others.  A quantile regression technique was used to investigate productivity effects of agricultural
extension and other farm inputs over the entire conditional distribution of farm yield residuals.

We find that productivity effect of agricultural extension is highest  at the extreme ends of
distribution of yield  residuals.  Complementarity of unobserved farmer ability with extension service
at higher yield residuals and the diminishing returns to the extension input, which are uncompensated
for by ability at the lower tail of the distribution, are hypothesized to account for this U-shaped
pattern of the productivity effect of extension across yield quantiles. This finding suggests that for
a given level of extension input, unobserved factors such as farm management abilities affect crop
yields differently. Effects of schooling on farm yields are positive but statistically insignificant. Other
determinants of farm yields that we analyze include labour input, farmer experience, agro-ecological
characteristics of farms, fallow acreage, and types of crops grown.  
Key words: agricultural extension, economic effects
JEL Classification: O13 and Q16