Not only is the equation of deaths to would-be births obviously flawed, the notion of quantifiable independent factors in decision to produce a child is excessively reductionist. There are not 8,000 couples who thought "I am 99% ready for a 3rd baby, but the car seats are the deal breaker"
also to your aside, japan has uniformly considerate, alert, and obedient drivers, more than i've experienced anywhere else. The only exception seemed to be foreign cab drivers.
If you read their methodology they are basically proving people made that exact decision. It very airtight. I can definitely see safety conscious or risk averse parents making that exact decision or the decision to delay a child and then never getting around to it.
also to your aside, japan has uniformly considerate, alert, and obedient drivers, more than i've experienced anywhere else. The only exception seemed to be foreign cab drivers.