The average labor income of 965 farmers in Black Hawk, Grundy and Tama counties in 1913 was $306 and the return on investment 4.1 percent. In the same area the average labor income of 210 farmers in 1918 was $1,382 and the return on investment 6.3 percent. War prices for farm products were the cause for the larger labor incomes the latter year.

Thirty-five percent of the farmers in 1913 and 19.2 percent in 1918 had minus labor incomes; 4.3 percent of the farmers in 1913 and 33.6 percent in 1918 had labor incomes of $2,000 and over.