But the other part of the theory is that these aborted fetuses would have been born to mothers, most likely single, who didn’t really want them. Such a toxic family situation would, the theory goes, be more likely to breed criminals. The book “Freakonomics” explains the theory in some detail.
As for it sounding like eugenics, that is a slippery slope type fallacy. Abortion has been legal for almost 40 years and I’m not aware of a single one that has been performed against a woman’s will.
One reason for the drop in violent I haven’t seen mentioned here is the wide-spread use of mandatory sentences for repeat violent offenders. This has certainly played a role.

It seems possible, I guess (the murder rate synchronizing with the abortion-rate), but also comes off as one answer among many coinciding social forces.

It seems to me that quantifying perception is too subjective to yield meaningful theories. But then again, it is only a theory.

As long as we’re theorizing about crime — here’s are somes areas I want someone with a research grant to look at: is there a measurable correlation between the income of crime victims and “perception of crime” in a city? is the “perception of crime” higher in Atlanta than it was in 2002 because new city residents who moved here from lower crime areas have a lower tolerance for crime than people who have lived in the city longer?

For instance, the murder rate could go to zero or overall crime stats could go way down, but if at the same time, home invasions or flat-screen thefts via break-n-enter go up in residential neighborhoods, both the perception and the reality is that regular folks are more likely become a crime victim despite lower crime rate statistics.