Figure 2-4. Total change in rural and farm populations in North America from 1930-2000. Source: USDA data; author elaboration.

Vogel, 2003). Along with the variation of the size of the hired workforce among countries, there is also consider­able variation between different sectors of agriculture and a concentration of demand for hired workers in vegetable, fruit and horticulture systems (Frances et al., 2005). The seasonality in these sub-sectors has encouraged the use of temporary workforces, but the nature of this workforce has itself been in flux for the last fifty years as conditions in the industry have changed. Temporary work in agriculture con­tinues to require minimal skills and be physically demand­ing with poor pay and poor work conditions.
     In the US this employment has traditionally been taken up by immigrant populations, which in the past have in­cluded Chinese, Japanese, Indian, Pakistani, Mexican and Dust Bowl migrants. The racial division between farm own­ers and farm workers has persisted; the 1997 US Census of Agriculture found 98% of US farmers were white and 1.5% Hispanic, but 90% of the hired farm workers were Hispanic (Martin, 2002). Hispanics living in rural areas are more likely to be working in lower skilled sectors such as agriculture and because of low wage levels are more likely to live in poverty than non-Hispanic whites (USDA-ERS, 2005a).
     Immigrant  agricultural populations  in the US  have been regulated with varying levels of success by means of a number of laws, recruitment schemes and immigration policies including the Immigration Reform and Control Act

(1986), which instituted the Special Agricultural Worker program and two guest worker programs (H-2A and Re­plenishment Agricultural Worker). These were intended to provide a legal work force that could join unions and result with better border control in reducing illegal immigration and creating better working conditions for the legal agri­cultural labor force (Martin, 2002). These objectives have not been realized given that in the first part of the decade an estimated 50% of all hired workers in crops and live­stock farming, 25% in meat processing and 17% in food services are undocumented or unauthorized workers (Wells and Villarejo, 2004; Passel, 2005; Simonetta, 2006). These changes have also been happening in the context of the in­fluence on international migration of the North American Free Trade Agreement (NAFTA), which came into force in 1994, although it did not formally include labor mobility as part of the framework agreement. The economic changes wrought by NAFTA have shifted relative economic power between the signatories to the agreement with differential effects on migration and on relative wage levels occurring among Mexico, USA and Canada (Canales, 2000; Aydemir and Borjas, 2007).

2.1.2 Changes in European farming and rural populations
Europe emerged from the 1940s with the sector predomi­nantly consisting of small "mixed" farms. As technology