Robert Verbruggen highlights what appears to be the same study I mentioned in January, although the researchers have increased the magnitude of the effect of teacher unionization on students’ future earnings:

We find robust evidence that exposure to teacher collective bargaining laws worsens the future labor market outcomes of men: in the first 10 years after passage of a duty-to-bargain law, male earnings decline by $2,134 (or 3.93%) per year and hours worked decrease by 0.42 hours per week. The earnings estimates for men indicate that teacher collective bargaining reduces earnings by $213.8 billion in the US annually. We also find evidence of lower male employment rates, which is driven by lower labor force participation. Exposure to collective bargaining laws leads to reductions in the skill levels of the occupations into which male workers sort as well. Effects are largest among black and Hispanic men.

Verbruggen expresses skepticism, as he should for a study that has a bit of that too-good-to-be-true feel for conservatives, but I’m not sure he’s considering the mechanisms.  For instance, he emphasizes that the study focused on men because (his words) “the labor market for women changed so dramatically in this time period.”  Having this ready excuse could lead one to be too quick to dismiss an underlying mechanism or indirect cause.

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For instance, from the 1987-1988 school year to the 2011-2012 school year, the percentage of public school teachers who were men dropped from 29.5% to 23.7% (or one out of every three to one out of every four).  If the same rate of decrease extends back in time, the percentage of male teachers at the beginning of the study window would have been much higher.  That could suggest that the apparent effects of teachers’ collective bargaining are actually effects of a changing workforce, or it could suggest that the demographic trend is a result of collective bargaining.

In any event, it will be interesting to see whether the ability of government school employees to avoid union membership will have an effect on the percentage of men in the classroom, the career results of students, or both.