even if we isolate factors that create more or less divorce, these insights would only yield policy recommendations if coupled with an understanding of whether we currently have an efficient number of divorces, too many, or too few.
The concept of an "efficient number of divorces" is distasteful, at least, to marriage advocates. Even if we allow that sometimes divorce is the least of the available evils, it is still an evil. In thinking about the efficient number of divorces, Stevenson and Wolfers raise the analogy with the "churn" in the labor market. However, leaving a job can be a matter of indifference to the worker, as well as to the analyst looking down from on high. Not so, I think, with leaving a marriage.
Marriage changes people more than any other voluntary institution. Marriage and divorce are not just arrangements for material advantage. Every marriage carries the hope of building up husband, wife, their children, even their whole lineage. Every divorce is a social loss because it dashes that hope. Economists don't count the social costs of dashed hopes for personal and social upbuilding. But we can.