high taxes ! cut federal taxes and cut property tax!
I mean, I love a tax cut too, but I don't think taxes per se are the reason why people aren't having kids.
This data is somewhat stale, but here's a graph of taxes as a % of GDP vs birthrate. Color and size are both tied to income here. But there's basically no relationship, and there are countries with high tax rates and high birth rates, and low tax rate countries with low birth rates. And if you play with the time slider, you can see that countries move left and right in terms of taxes relatively quickly, but across countries most data point are drifting slowly down in birth rate.
https://www.gapminder.org/tools/#$model$markers$bubble$encod...