I read through the underlying paper, and I don't quite understand their methodology. It seems like they're taking a bucketload of demographic information and then trying to control for every other possible factor that could affect fertility rates to isolate the effect of car seat laws. I'm skeptical that it's even possible to control for all of those variables. Even assuming that they perfectly model the factors they do account for, it's perfectly possible that there are more underlying factors.
Additionally, interpreting the results as t-statistics doesn't really tell us very much, as the variation between model and reality could easily be noise from the control variables rather than from a relationship between car seat laws and fertility.
I'm not saying the paper doesn't have any merit at all--I think the idea is quite interesting. I am just skeptical of inferring anything from the results, given that the methodology is very poorly described (and is so error-prone).
Additionally, interpreting the results as t-statistics doesn't really tell us very much, as the variation between model and reality could easily be noise from the control variables rather than from a relationship between car seat laws and fertility.
I'm not saying the paper doesn't have any merit at all--I think the idea is quite interesting. I am just skeptical of inferring anything from the results, given that the methodology is very poorly described (and is so error-prone).