The authors rely on several different data sources to tackle the problem of estimating whether IRCA has had an impact on illegal immigration to the United States and employ a variety of approaches to tease out information on trends. Some present results based on data collected in Mexico, the single most important source country-important as a supplement to get a complete picture of changing patterns of illegal immigration. In addition to the volume editors, contributing authors include "Robert Warren, Thomas J. Espenshade, Michael J. White, Douglas S. Massey, Jorge A. Bustamante, "and àIWayne A. Cornelius.