U.S.-Mexico border manifests from the 1920s indicate that Mexicans migrating to the United States then tended to be healthier, wealthier and more productive than those who did not migrate, according to CU-Boulder researchers. Their results suggests that U.S. migration policy in the early 1900s created an environment that drew “economically strong” Mexicans to migrate to the United States, and they say the findings have implications for contemporary policy.