SEMAINE D'ÉTUDE SUR LE ROLE DE L ANALYSE ECONOMETRIQUE ETC. 115] 
tural population in a low income or underdeveloped economy 
will have to occur at approximately the same rate as the growth 
of total population unless per capita food consumption is to 
decline. Labor cannot be released to other sectors of the eco- 
nomy for their development and real factor costs of food would 
not decrease. In fact, unless additional land can be brought 
ander cultivation or land developed through irrigation or recla- 
mation at the same rate as the population grows, average output 
per worker in agriculture may decline and real factor costs of 
food may increase. 
There are circumstances in which an unchanged production 
function is consistent with increased output and lower marginal 
costs of production. If the marginal product of labor is sub- 
stantially higher in certain nonfarm pursuits than on the farm, 
the availability of certain manufactured inputs that may be 
ased in agriculture may permit an increase in output per unit 
of farm labor and a transfer of labor from agriculture to the 
nonagricultural sector. This is a possible explanation of the 
impact of a new and cheaper source of fertilizer (the partial 
replacement of manure, fish, fish meal, and cottonseed meal 
by chemical fertilizers in Japan), the replacement of feed by 
petroleum products to produce power, or the transfer of certain 
functions performed on farms to firms that can specialize to 
a greater extent (churning butter, tanning hides. retting flax, 
or butchering livestock). 
There is evidence that for the half century from 1880 to 
[930 in the United States the ratio of total output to input did 
not change significantly, while there was an increase in the 
output per unit of labor and per unit of land (real estate) 
ng: Farm employment increased from 2.2 to 6.6 million; farm employment 
1s a percentage of total population changed only from 21.5 to 19.79. 
Estimated gross output per farm worker increased by only 11% in the 
to-year period. There are some indications, admittedly crude, that national 
der capita income increased onlv moderately during the four decades 
>| 
Johnson - pag. 
I)