The nation has had a long history of guest worker programs targeted at the agricultural industry, which have enabled farmers to temporarily import foreign workers to perform seasonal jobs without adding permanent residents to the U.S. population. Unsuccessful attempts were made during the past few Congresses to amend the H-2A program, the only means currently available to employers who want to legally utilize aliens in temporary farm jobs. Recent interest among some Members of Congress in a broad-based guest worker program has renewed efforts to enact legislation that relates specifically to the agricultural sector. The elements of the debate concerning an agricultural guest worker program have changed very little over the years. Its principal points are twofold: whether there is an adequate supply of workers in the United States to fulfill the widely fluctuating labor requirements of some farmers; and whether the temporary admission of aliens to perform seasonal farm jobs adversely affects the labor market prospects of domestic workers. Growers of perishable, labor-intensive crops (e.g., fruit, vegetable, and horticultural specialty products) whose demand for directly hired and contract workers typically peaks during the harvest season argue that they need access to foreign labor because insufficient U.S. workers are available at that time. They assert that importing workers to perform seasonal farm tasks does not harm U.S. workers because the two groups do not compete. In other words, they contend that domestic workers are largely unwilling to perform the farm work in question—even if higher wages were offered them. Domestic workers, it is claimed, have more attractive alternatives to seasonal farm employment (e.g., nonfarm jobs arguably are less strenuous and dirty as well as more stable and prestigious). Without access to foreign labor, grower advocates maintain that crops could not be harvested; consumer prices would rise due to the reduced supply of U.S.-grown produce; and the nation would become more dependent on low-wage foreign competitors for a portion of its food supply. Farm worker advocates contend that if growers raised wages and improved working conditions, more domestic workers would be willing to accept seasonal farm employment. They assert that the employment and wage prospects of domestic workers are depressed by additions to the U.S. labor supply through guest worker programs. It is argued that these programs also harm similarly employed U.S. workers by weakening incentives to develop and adopt innovations that improve their working conditions and labor-saving technologies that increase their productivity (and hence, the wages of a smaller workforce). Opponents of temporary alien worker programs further declare that growers prefer foreign over domestic workers because the former are not covered by the same laws as domestic workers (e.g., Migrant and Seasonal Agricultural Worker Protection Act, Unemployment Insurance, and Social Security); are less demanding due to lower wages and poorer working conditions in their home countries; and are easier to control because they cannot easily work for another U.S. employer if the grower terminates them. The remainder of this report focuses on the impact an agricultural guest worker program might have on U.S. workers. The adequacy of the domestic supply of farm workers is addressed in another CRS Report. Fundamentally, the debate over the effect on U.S. workers of temporarily admitting foreign workers centers on whether an increase in the supply of labor reduces the wages and employment of domestic workers. Economic theory can help clarify this debate. Before the entrance of foreign workers to the U.S. labor market, the amount of labor that domestic workers are willing to supply to employers is represented by the curve labeled S1 in Figure 1 . It is upward sloping because workers are willing to supply more labor services in response to higher wages. Employers' demand for labor is represented by the curve labeled D, which slopes downward because employers are willing to employ more workers at lower wages. Equilibrium in this labor market occurs at point A, where those willing to work for wage W 1 equals employer willingness to hire at that wage. In the absence of foreign labor, then, U.S. farm employment is equal to E 1 and U.S. farm workers' wage rate is equal to W 1 . The addition of foreign workers expands the total quantity of labor at any given wage rate. This is represented by the rightward shift of the supply curve to S2, with the additional labor represented by the difference between S1 and S2. This increase in the labor force will only find employment if the wage falls, for only at a lower wage will employers be willing to hire more workers. Thus, equilibrium after the importation of labor occurs at point B, where the wage rate of domestic and alien farm workers drops to W 2 and employment of domestic and alien farm workers expands to E 2 . In summary, the theory of supply and demand predicts that the wage rate for all workers falls from W 1 to W 2 after the entrance of foreign workers to the U.S. labor market. As a result of the drop in wages, total employment expands from E 1 to E 2; domestic employment contracts from E 1 to E 3 ; and alien worker employment is equal to E 2 minus E 3 . Because the lower wage (W 2 ) makes farm work less rewarding, some domestic workers likely will look for jobs outside the agricultural sector. Employment of domestic farm workers accordingly will decline (from E 1 to E 3 ). While the total employment of foreign workers (E 2 minus E 3 ) expands, a portion is at the expense of the farm jobs formerly held by domestic workers (E 1 minus E 3 ). This is called the displacement effect . The size of the displacement effect depends on the shape of the labor demand and domestic labor supply curves. Along with lower domestic employment in agriculture, the presence of foreign farm workers reduces the amount of wages that accrues to domestic farm workers. Because the addition of foreign workers also expands output, agricultural prices are expected to fall and thereby benefit U.S. consumers including domestic farm workers. Authorized under the Immigration and Nationality Act at Section 101(a)(15)(H)(ii)(A) as modified by the Immigration Reform and Control Act of 1986 (IRCA, P.L. 99-603 ), the H-2A program was begun in 1952. It allows an unlimited number of foreign workers to temporarily enter the United States to fill seasonal farm jobs at employers who demonstrate the existence of labor shortages by undertaking recruitment efforts prescribed by the U.S. Department of Labor (DOL). Principally East Coast growers of perishable labor-intensive crops, who largely did not utilize the Bracero program, were the original applicants for H-2A workers. The H-2A program "was able to escape the heavy criticism levelled against the Bracero program primarily by keeping a low profile." In other words, there were a great many more braceros than H-2A workers when both the Bracero program (1942-1964) and H-2A program (1952-present) were in effect. (The Bracero program is discussed below.) Despite increases in H-2A worker certifications issued by the U.S. Department of Labor in recent years, the number of H-2A workers remains quite small compared to the nearly 1 million hired farm and agricultural service workers employed in 2008. Thus, even if the labor certification process has not operated as intended—to protect similarly employed U.S. workers—the H-2A program's low utilization suggests that its overall impact on the domestic farm labor force has been minimal. However, the reliance on the H-2A program of tobacco, fruit (e.g., apple, peach, and tomato), vegetable (e.g., onion and squash), and grain growers in some states (e.g., North Carolina, Virginia, Kentucky, Idaho, California, and Texas) might have had a more substantial effect on domestic farm workers in certain local labor markets. Some proposals to modify the H-2A program either by legislation or regulation might make it easier for growers to temporarily employ foreign workers. Farmers, as a consequence, would likely import more H-2A workers than they had previously. Given authorized aliens' potentially greater share of the hired and contract farm labor force as a result of changes to guest worker policy, it appears that the effects of the Bracero program on domestic farm workers are more relevant than the (unquantified) effects of the H-2A program. At its peak in 1956, the Bracero program allowed some 445,000 Mexican workers to take temporary jobs in the U.S. agricultural industry. The few studies that tried to empirically estimate the labor market impact of the Bracero program are examined below. Morgan and Gardner examined a seven-state area, in which more than 90% of braceros had been employed, to estimate the impact of the program on the wage and employment levels of hired farm labor. Its effect was found to be consistent with economic theory: the Bracero program increased total farm employment, reduced employment of domestic farm workers, and lowered the farm wage rate. Morgan and Gardner concluded that the wage loss to all nonbracero farm workers was 6% to 7% of total wages paid to farm workers in the bracero-using states between 1953 and 1964, or some $139 million per year (in 1977 dollars). U.S. farmers were found to have gained from the program by being able to hire about 120,000 more workers at 15-20 cents less per hour than they would have in the program's absence. Such a large employment response (about 26%) to a much smaller decrease in wages (less than 9%) is consistent with the informal observation that braceros were a substitute for mechanization, notably in High Plains cotton, and that the end of the program substantially accelerated the mechanization of Texas cotton. This is also the period in which the tomato harvester came into widespread use in California.