156 PONTIFICIAE ACADEMIAE SCIENTIARVM SCRIPTA VARIA - 28 
demand for farm products (assuming little international trade) 
will be about 3.5% per annum. Even if half of the increased 
output is due to increased quantities of nonlabor inputs, the 
ratio of output to input must increase by about 1.5%, each year. 
This implies a doubling of the output-input ratio in about 45 
years; in the last 50 years the output-input ratio has increased 
by about 75% in the United States. 
I should hasten to add that it is not essential for the absolute 
level of farm employment to remain stable during the early 
period of industrialization. The usual pattern has been for the 
farm labor force to increase absolutely for several decades 
after per capita incomes have started to increase. In fact, if 
an economy starts from a position of, say, 80% of its labor 
force engaged in agriculture and if total population is increas- 
ing by 29%, per annum, it would be nearly impossible for non- 
farm employment to absorb all of the increase in labor force. 
Under these assumptions, the nonfarm labor force would have 
to grow at a 10% annual rate or double about every 7 years (!). 
In this section I have tried to indicate briefly some of the 
interrelationships between the supply of agricultural products 
and the process of economic development. It has been indicat- 
ed that an improvement in the output-input ratio is required 
before rising per capita incomes can be achieved in a low 
income area. It has also been indicated that if population 
growth is moderate or high and the income elasticity of de- 
mand is high that the increase in the output-input ratio must 
be a significant one if agriculture is not to act as a restraint 
on economic growth. It also was indicated that while farm 
employment must decline as a share of total employment, it 
may increase absolutely during the early period of industrial- 
ization. 
(') Such a growth cannot be said to be impossible; between 1926 and 
1934 the annual increase in nonfarm emolovment was about 09% in the 
Soviet Union 
16] Johnson - pag. 16