[Excerpt] As the 21st Century commences, immigration has once again become a major source of the nation's labor force growth. The public policies that enable mass immigration to occur do more than simply increase the size of the nation's labor force; they also affect such key compositional matters as its human capital, demographics, and geographic attributes. Immigration policy, however, has more than just immediate economic consequences; it also helps to mold the nation's future as long-term citizenship obligations are usually involved.