Reformers gravitate towards seemingly simple "solutions". Too much crime? Ban guns. Too much smog? Many would, of course, love to ban cars but that may be even more tricky than trying to ban guns. So what can be done "to get people out of their cars?" Get them to live at higher densities. Easy. Well, no. Most Americans like their cars and their spacious living. Alas, many years of "smart growth" plans have had almost no impact.

The most interesting evidence is from abroad where policies are different and where the people are surely more sensible than here.

USC colleague Gen Giuliano (with grad student Dhiraj Narayan) looked at a large sample of travel diaries from the UK and found that, "how people travel in Britain has very little to do with low-, mid-, or high-density living."

Another USC grad student, Bumsoo Lee, and I compared settlement trends in Canada with those here. We found that, as in the U.S., jobs and people are suburbanizing -- in spite of even tougher policies in Canada to get people to do the right thing.

Social engineering is very hard work because people's preferences find a way of being honored. It's not easy being Green.