The history of US agriculture from 1940 to the end of the 20th century is characterized by remarkable gains in productivity, increased specialization in high-value crops, and rapid technological advancements, particularly in mechanization and automation. These developments significantly reduced the need for manual labor in farming, accelerated the reallocation of workers from agriculture to industry and services, and contributed to substantial growth in income per capita.

Although the US was already an industrial nation in 1940, roughly 20 percent of the labor force was still employed in agriculture. The education, literacy, and skills of farmers were crucial in facilitating the adoption of improved agricultural methods and technologies in the following decades. The diffusion of machinery and chemical fertilizers, along with the shift toward more valuable crops, increased productivity per acre; however, the extent of this increase often depended on farmers’ ability to learn and implement new practices. A growing body of research has demonstrated a strong link between farmers’ education and their adoption of technology.

By 1940, Japanese Americans (both first- and second-generation) represented an exceptionally skilled segment of the agricultural workforce in the western United States. According to the 1940 Census, more than 20 percent of all Japanese Americans were farmers or farm workers, with many operating highly productive farms on the West Coast. Their success came not only from their higher levels of education compared with other groups but also from their strong work ethic, openness to innovation, and expertise in crop-specific techniques. Japanese Americans held agricultural work in high esteem, using their skills to specialize in valuable crops such as artichokes, asparagus, cabbage, garlic, onions, and various fruits and vegetables.

Shortly after the US declared war on Japan following the Pearl Harbor attack on December 7, 1941, the government cited national security concerns to forcibly evacuate more than 110,000 people of Japanese ancestry from the West Coast between March 2 and October 31, 1942. The relocation program targeted both first- and second-generation Japanese immigrants, removing almost the entire population from the exclusion zone. Most relocated Japanese Americans were interned in relocation centers from 1942 to 1945, and most of them never returned to their original occupations or places of residence. Consequently, this policy quickly reduced the local supply of highly skilled agricultural workers and managers on the West Coast.

Our research examines the effects of excluding Japanese Americans from farm work on the growth of farm values and output, the adoption of new technologies, and overall economic and population growth. We used county-level data from the US Census of Agriculture between 1920 and 1960 and compared counties in the exclusion zone with those outside it before and after 1942, leveraging differences in the share of a county’s population that comprised Japanese farm workers in 1940.

Specifically, our findings suggest that, by 1960, the removal of Japanese residents from the exclusion zone reduced the growth of farm values by 12 percent for every one percentage point of the county’s population that consisted of Japanese farm workers in 1940. In contrast, between 1945 and 1960, farm values in counties outside the exclusion zone with a high share of Japanese farmers grew faster than those with a low share by a similar ratio. This indicates that the relocation program removed the advantage that high-skilled Japanese farmers had given to local agriculture within the exclusion zone.

We also found that counties that lost a greater proportion of Japanese farmers relative to their 1942 population experienced slower growth in value per farm, but not in the number of farms. This suggests that while other farmers may have replaced Japanese farmers, they generated less value per farm. Furthermore, the average value of harvested crops per farm declined more markedly in counties that lost a higher proportion of Japanese farmers, indicating a reduction in agricultural productivity.

Additionally, counties that lost a large share of Japanese farmers also experienced slower growth in fruit and vegetable production, reduced their use of modern fertilizers, and adopted fewer tractors, motor trucks, automobiles, and telephones. This technological lag was primarily driven by the loss of Japanese farmers with high school education and those who were responsible for farm management and technology adoption. These findings are especially significant given that US agriculture underwent rapid productivity growth and technological transformation after 1940. Improved seed varieties and the widespread adoption of fertilizers and machinery drove agricultural productivity growth to unprecedented rates between 1940 and 1980. Moreover, farms began to consolidate during this period, with intensive, high-productivity farms becoming prevalent, along with highly specialized products grown in greenhouses and nurseries. Therefore, regional differences in the ability to adopt agricultural technologies during this period may have had long-term effects on farm productivity growth. Finally, our findings reveal that declining agricultural productivity led to decreased agricultural employment in affected counties, as well as slower growth in total employment and population.

NOTE
This research brief is based on Peter Zhixian Lin and Giovanni Peri, “How the 1942 Japanese Exclusion Impacted US Agriculture,” National Bureau of Economic Research Working Paper no. 33971, June 2025.