1150 PONTIFICIAE ACADEMIAE SCIENTIARVM SCRIPTA VARIA - 28 
areas is approximately #59, greater than for the industrial 
areas. In the low income areas, despite the high income elasti- 
cities and modest increases in per capita income, most of the 
increase in demand results from population growth. If Latin 
America were to have a 39, annual increase in GNP per ca- 
pita, the demand growth for food would be in excess of 49, 
annually. This would require a doubling of food output in 
about 18 vears. 
C. Economic Development and the Supply of Agricultural 
Products 
In the discussion of the general frame-work of the relation- 
ship between agriculture and economic development the discus- 
sion of changes in supply were largely in terms of output chan- 
ges that had to occur if economic development were to occur. 
[t is time now to turn to a discussion of the major factors that 
lead to output increases. The following classification includes 
nothing that is new, but is useful for organizing our discus- 
sion. Increased agricultural output occurs as a result of one 
or more of the following: 1) increased use of inputs; 2) im- 
proving the quality of inputs; 3) increased knowledge or a 
change in the production function, and 4) a change in incentives 
for farm operators and their families. 
If all of the increased output must come as a result of 
increased labor and land, it is unlikely that agriculture will 
be able to make any significant contribution to economic de- 
velopment (1). If this is the case. the growth of the agricul- 
(') This observation may well have been correct for the United States 
in the period before 1860. Given the large quantity of land that was avail- 
able for settlement, it was possible to expand output of farm products 
without changing the relative combination of land to labor. Admittedly 
scanty evidence for the period from 1820 through 1860 indicates the follow- 
161 Johnson - pag. 10