“[A] ‘temporary-only’ approach to immigration reform suffers from serious shortcomings, most obviously in the case of undocumented immigrants already in the United States. Roughly 35 percent of undocumented immigrants have lived here for 10 years or more, 1.6 million are children, and another 3.1 million U.S.-citizen children have at least one undocumented parent. As a result, attempting to fit all of the currently undocumented population into a temporary worker program that lacks a pathway to permanent residence raises the specter of serious social and economic upheaval in the communities where undocumented immigrants live and the businesses where they work. Moreover, a rigid, temporary-only approach to immigration reform fails to adequately address the many factors which continue to drive undocumented immigration.”