The economic boom of the late 90s isn’t even mentioned as a possible cause–perhaps because it can’t explain why the improvement continued after the bust of 2000. But it’s not hard to come up with at least three unmentioned theories that don’t have that problem: 1) Lead removal. The argument that removing lead from the environment lowered pathological behavior is controversial, but it roughly fits this timeline, no? 2) Social networking. Maybe all the new Internet connectedness is more good than bad, giving people who would be swamped parents or social misfits in earlier eras new communities and relationships; 3) [yes] Welfare reform. When the 1996 reform law passed, opponents on the left predicted a rise in domestic violence. The reverse seems to have happened. Why? Could it be because unprecedented numbers of women from the most at-risk families–poor single-parents–went into the labor force, and work turns out to be a centering, de-isolating, generally healthy experience? (That’s a suggestion backed up in Jason DeParle’s American Dream.)
These all could be BS explanations. But they seem at least as plausible as “increasing effectiveness of services.”