LAW enforcement officials, politicians and social scientists have put forward many explanations for the astonishing drop in crime rates in America over the last decade or so, and yet we remain mystified. Studies have shown that while each of the usual suspects — a decline in crack use, aggressive policing, increased prison populations, a relatively strong economy, increased availability of abortion — has probably played some role, none has proved to be as dominant a factor as initially suggested.
Perhaps we have been overlooking something obvious — something that our implicit biases caused us not to notice.

My unusual suspect is foreigners: evidence points to increased immigration as a major factor associated with the lower crime rate of the 1990's (and its recent leveling off).

Fascinating! You mean that all that name-calling and meta-politics actually was bullshit? Who knew!?