The inspiration for this book came from a collaborative research project on immigration, begun in 2001, when we were colleagues at University of Nebraska- Lincoln (Bodvarsson was a Visiting Professor there in 2001-05). Our project dealt with the application of Say's Law to the supply of immigrant labor, meaning that when the supply of immigrant labor grows in an area, the new immigrants, being consumers, bolster labor demand and help to offset the lower wages they may bring about. Our test case was the seemingly obscure Dawson County, Nebraska, where the meatpacking industry experienced a relatively huge increase in Hispanic-born labor supply around 1990. We found for Dawson County this ``demand effect'' to be signi?cant and our results for this test case generalizable to other, more prominent, test cases. This inspired us to study the famous Mariel Boatlift, where Miami's labor force grew suddenly by 7% due to the arrival of nearly 125,000 Cuban refugees in the spring of 1980. In that study, we showed that the Marielitos exerted a signi?cant demand effect, which we argue helps to account for the stylized fact that the Mariel in?ux had a relatively benign effect on the Miami labor market. We had the privilege of presenting both studies at various conferences in the USA, Norway, Taiwan and Israel, and these studies have been published in Labour Economics and the Research in Labor Economics series (both studies are discussed in detail in this book).