I recently finished The Great American Crime Decline by criminologist Franklin Zimring. It's a judicious discussion of possible reasons for the 1990s decline in crime that pays considerable attention to the famous Levitt/Donohue idea that the availability of abortion post Roe v. Wade led to lower crime rates years later as a generation of wanted children came of age. Zimring is skeptical, partly because examination of pre and post Roe data shows increases rather than declines in categories, such as the proportion of babies born to unwed teenage mothers, that would logically be associated with unwanted children. He's also skeptical because in Canada, which had a crime decline in the 1990s similar to the US (despite not increasing its incarceration or policing levels), there wasn't the US tilt toward crime rates going down especially fast among younger offenders that Levitt and Donohue use to support their claim.
I'm sympathetic to Zimring's conclusion that both purely demographic explanations (a lower proportion of young males) and rational choice explanations like incapacitation, general deterrence, policing quality and quantity, and Levitt and Donohue's leave a great deal of the 1990s crime decline unexplained. I'm less than sure, though, about his claim that the 1990s decline occurred without a substantial change in the social fabric of American big cities, in which the decline was especially striking.
My candidate, unmentioned by Zimring, for a significant demographic plus cultural explanation for 1990s US and Canadian crime declines, especially in certain big cities, is large-scale, ongoing immigration to both the US and Canada over the past several decades. Contrary to a rational choice analysis, which would all else equal expect high immigration to create more crime among low-SES native-born residents of US and Canadian cities who compete with new immigrants for jobs, I think there is a value competition story to tell about how the arrival of waves of immigrants to the US from the 1970s on has enabled the growth over time of a working-class culture of pride and disdain among low-SES native-born Americans and Canadians ("we play by the rules instead of coming illegally; we know the language; we don't wait on the street for work; we're real Americans/Canadians" ) that was not possible when there was no large-scale new immigration to US and Canadian cities from Latin America, the Caribbean, Asia, and Africa. To put it in VC-speak: It's worth developing and trying to test the hypothesis that egoistic values encouraging deferral of immediate gratification for long-term gain and altruistic values encouraging adherence to the rules of criminal law have gained some ground among low-SES, non-immigrant Americans and Canadians. A poor young black man in New York, Chicago, or Compton, California whose family has been in the U.S. for centuries and who has come of age from around 1990 to the present has grown up in a group that lacks the clear bottom-of-the-totem-pole position that applied to his father's generation of poor black Americans, and that has plausibly made a positive difference in fostering working-class values over crime. For new immigrants themselves, there is a very plausible rational choice story about a desire to avoid criminal problems that could result in deportation; for them, too, though, one could tell a value competition story about their having their own combination of pride and disdain relative to low-SES native-born Americans and Canadians ("we work hard; our families stay together; our women are honored") that is also conducive to the avoidance of criminal behavior.
To test the VC hypothesis just suggested, it would be interesting to have longitudinal attitudinal data, including ethnographies as well as surveys; an updated version of Talley's Corner, Elliot Liebow's 1968 study of lower class black men in Washington, D.C. would be extremely interesting.
One easy thing to do: It's interesting to take Table 1.1 in Zimring's first chapter, which shows the ranking of the fifteen biggest U.S. cities in reducing crime in the 1990s, and relate it to the proportion of foreign-born residents in the city in 2000, which I calculated from the census website:
1. New York City .36 2. San Diego .26 3. San Francisco .37 4. Dallas .24 5. Los Angeles .41 6. Houston .26 7. San Antonio .12 8. San Jose .37 9. Chicago .22 10. Indianapolis .05 11. Phoenix .19 12. Detroit .05 13. Columbus .07 14. Philadephia .09 15. Baltimore .05
Like most social science relationships, it's not an air-tight one, but it's pretty strong. For each 10% increase in its foreign born population, a big city is expected to do 2.7 ranks better in its level of crime decline; the correlation between % foreign born and excelling in crime decline is .79, so over 60% of the variance is explained. Obviously, a more thorough analysis would need to control for other factors (e.g., whether cities with higher foreign born populations also have higher economic growth, and what proportion of greater crime declines in high foreign born cities is associated with low crime among the new immigrants themselves), but the quick and dirty analysis suggests that the effect of immigration on crime by old-timers as well as newcomers is at the very least worth looking into further. That project can be carried out with or without a value competition focus; a value competition emphasis on a possible growth of egoistic and altruistic values among low-SES native-born Americans and Canadians in response to an influx of new immigrants is one way, but of course not the only way, to interpret the data.