> And a team of economists have now crunched the data proving that zoning and restrictive land-use regulations–forces that contribute to making housing so expensive in cities like San Francisco and New York–are actually driving fertility rates downward.

Are they actually preventing couples from having children, or are couples simply moving away from those areas in order to have their children elsewhere?

And on top of that, are the kind of people who move to NYC or SF already the kind of people planning not to have a kid over the next 5-10 years, or ever?

Taking a quick look at the original paper, the authors don't appear to address these potential factors at all.