Gallagher, part 4

To recap: Changing divorce law did not only affect the "exit requirements" from marriage, it affected the shared vision of what marriage consists of, what the marriage vow means. The law names the reality of who is married and who is divorced in a way with which merely private definitions have a hard time surviving, much less competing.
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We don't, in my view, have very good social science tools to measure cultural effects caused by law for a variety of reasons. Individual and private communties resist or adopt the new meanings promoted by legal change at differential rates, for example.

So, for example, despite the law's change, older views of marital permanence persisted privately for some time — up into the mid-80s, family lawyers report they would still occasionally run into clients who would utter bits of 1950s movie dialogue like: "I'm not giving him a divorce!" As if they had a choice.

It takes a while for the new meanings encoded by the law to percolate and permeate the culture. Also, the law in one state can certainly affect the cultural meanings in another states (making isolating the effects of legal change more problematic). If polygamy were legal in, say, Oregon, that would almost certainly affect the understanding of marriage in Massachussetts. Monogamy might remain the most common public understanding of marriage, but, by definition, no longer a core or essential feature of marriage in American society. Similarly, when California adopted unilateral (no-fault) divorce, something visible had changed in our understanding in the U.S. of what the marriage vow meant — even if it was another ten years or more before say, Louisiana adopted a similar law.

So, yes, correlation is not causality. But consider acquiring another proverb: Do not mistake all we can accurately measure for all that is real.