1152 PONTIFICIAE ACADEMIAE SCIENTIARVM SCRIPTA VARIA - 2§ 
The increases in the two average products were apparently 
due to increased purchases of nonfarm products, which were 
apparently cheaper than the farm inputs they replaced. While 
farm labor increased absolutely over the period, farm labor 
declined as a percentage of the total labor force from 49 to 21%. 
The United States situation as of 1880 is one that is not 
likely to be duplicated in any of the current low income areas 
of the world. U.S. per capita income was already at a relati- 
vely high level (about $400 in 1929 prices) and the income 
elasticity of demand for farm products was probably 0.5 or 
lower. About a fifth of farm output was exported, thus do- 
mestic consumption could increase more than domestic output. 
TABLE 2 
Indexes of Output, Inputs, and Productivity, United States Agri 
culture, 1880-1020 (!) 
(1847-49 = 100) 
Indexes 
Farm Output . . 
Production Inputs . 
Farm Labor . 
Farm real estate 
All other . 
Productivity 
Output/labor . 
Output/real estate 
1880 
7 
. 
+ 
1890 
43 
€ 
27 
62 
1900 
56 
72 
Ge 
1910 
61 
22 
1920 1930 
70 72 
23 97 
Ia% 137 
v 96 
53 62 
75 74 
45 48 52 
6h 72, 75 
M) Source: RarrH A. Loomis and GLEN T. BarToN, Productivity of Agri 
culture, United States, 1870-1058. USDA. Tech. Bul. No. 1238 (April. 
[961), pp. 57, 38. and 6o-6T 
But when per capita incomes are low and the income elasti- 
city of demand for food is almost unity, agricultural employ- 
ment must increase absolutely and remain a relatively stable 
percentage of total employment unless technological change 
occurs. 
16] Johnson - pag. 12