In an August, 2011, study from the Migration Policy Institute, authors Marc R. Rosenblum and Kate Brick address the acceleration of migration from Mexico and Central America’s “Northern Triangle” (El Salvador, Honduras, and Guatemala) from 1 million persons in the 1970s to about 14 million today. They trace U.S. immigration policy across three major migration periods over the past century and how growth and diversification of these immigrant populations have been functions of structural factors, policy decisions, and the interaction between them. The authors indicate how these changes contribute to the current controversy over U.S. immigration and create a challenge for today’s policymakers to reform the current immigration system and avoid or minimize future unintended consequences. The report is US Immigration and Mexican/Central American Migration Flows: Then and Now and is found here.