For more than a decade, it has been documented that Northern European countries do better at moving poor people up the ladder than the United States does. Some have dismissed these findings, pointing out that the United States cannot be compared with places such as Denmark, an ethnically homogeneous country of 5.5 million people. But Miles Corak of the University of Ottawa points out in his contribution to the Journal of Economic Perspectives that Canada is a very useful point of comparison, being much like the United States. (The percentage of foreign-born Canadians is actually higher than the percentage of foreign-born Americans, for example.) And recent research finds that people in Canada and Australia have twice the economic mobility of Americans. (The British are about the same as Americans but much worse than Canadians and Australians. )

What’s intriguing is that many of the factors that seem to explain the variation across countries also help explain the variation across the United States. The most important correlation in the Harvard-Berkeley study appears to be social capital. Cities with strong families, civic support groups and a community-service orientation do well on social and economic mobility. That’s why Salt Lake City — dominated by Mormons — has mobility levels that compare with Denmark’s. This would also explain why America in general fares badly; the United States has many more broken families, single parents and dysfunctional domestic arrangements than do Canada and Europe.