Immigrants to the U.S. are partially to thank for a dip in crime in this country. That's according to a new study out of CU-Boulder. The national crime rate started to go down in the early 1990s. That's about the time substantial numbers of new immigrants, legal and illegal, began to arrive. Sociology professor Tim Wadsworth is confident there's a link between those two trends. He's spent 15 years studying changes in the crime rate. Wadswroth speaks with Ryan Warner.