"U.S. employers in various industries argue that they need to hire foreign workers to perform low-skilled jobs. A threshold question about importing temporary lower-skilled workers, sometimes referred to as guest workers, is whether U.S. employers need foreign workers for lower-skilled positions, or whether there is a sufficient number of available U.S. workers who could fill these jobs. This question gains salience in times of high U.S. unemployment. The issue of whether U.S. employers need foreign workers is often stated in terms of whether there are domestic labor shortages in particular industries and occupations. Questions about the existence of labor shortages are difficult to answer definitively because of various factors." - CRS, Dec. 13, 2012.