> The largest effect they observed suggested that a one-year increase in spacing improves reading scores for older children by 0.17 SD—which would be three times the effect of increasing annual family income by $1,000.
In other words, instead of having your kids back to back, you wait a year ... and that's equivalent to $3000 of extra family income.
OK.
Earning 3K extra a year is ridiculously easy. Far more so than worrying about family planning. All I have to do is earn an extra $10 a day. If we split that between my wife and myself, that's an extra $5 a day. I'd rather focus on that. On top of it all, I can actually spend that money ... I can't spend 1 year.
I'd guess that 3k of income is at levels of the median or average family, where it actually matters. 40k vs 43k, that extra $3k might buy your family something important. Whereas at competent hackers income levels, I'd bet the marginal contribution of $1k toward children achievement is a lot lower. The difference between 120k and 123k is much less important.
Parental income and child intelligence are correlated, but the direct causal relationship is (I suspect) extremely weak except at the low-end extreme. The real relationship between these two variables is dominated by parental intelligence: smarter parents have smarter children (with a very strong correlation), and smarter parents earn more money (with a reasonably strong correlation).
Once the parents are picked, earning a little more money won't do much to make the children smarter. If anything it might make them dumber, since those extra hours spent at work are much better spent with your children.
> "Earning 3K extra a year is ridiculously easy. Far more so than worrying about family planning."
Take the time to look up other consequences of short birth spacing. Infant and maternal mortality, low birth weight, and a whole host of other complications become dramatically more prevalent as birth spacing drops below 2 years.
The academic results given here are just another part of the larger pattern: it's usually healthier to space births out 2+ years.
That assumes both that the increase in reading scores due to increasing family income is linear, and that annual family income and birth spacing are completely independent of each other.
In other words, instead of having your kids back to back, you wait a year ... and that's equivalent to $3000 of extra family income.
OK.
Earning 3K extra a year is ridiculously easy. Far more so than worrying about family planning. All I have to do is earn an extra $10 a day. If we split that between my wife and myself, that's an extra $5 a day. I'd rather focus on that. On top of it all, I can actually spend that money ... I can't spend 1 year.