A new study published Monday by the National Bureau of Economic Research argues against the first interpretation, showing that between 1997 and 2012, areas that experienced fracking booms — and therefore increased wages and economic opportunity for the less-educated — experienced a spike in birth but not marriage rates.

Why it matters: Though there is some evidence that falling working-class marriage rates were in part caused by shrinking economic opportunity, these results poke a hole in notion that better job opportunities will lead to more marriage.