Tuesday, October 23, 2012

Better educated twins live longer

What is the secret to a long life? A healthy life style, good nutrition, few worries, few risks, little stress. That is all obvious. When you look at data, life-span has a very high correlation with income, education, and other measures of standard of living. Of course, none of this implies causation, if fact one may think that an expected longer lifespan leads people to get more education. Enter the twin studies.

Petter Lundborg, Carl Hampus Lyttkens and Paul Nystedt use twins, who have the same genes and where subject to the same starting conditions, to disentangle what leads to longer lives. Education comes here as a clear winner. Even differences between twins like birth weight cannot make this disappear. Having more than 12 years of education gives you a bonus of 2-3 years, whether male or female.


O.K. said...

An obvious caveat in the twin studies design is the basic assumption that all unobservables are the same between twins. But if all of the unobservables are the same why would the twins end up with different education?

An example: think if one of the twins was dropped on her head as a kid and ends up being dumber. The dumber twin might leave school earlier, but might also die earlier because of the head trauma in youth. Their identification strategy is not immune to this. It may even be that their result is entirely driven by this.

Anonymous said...

If I understand correctly, the fact that they get the same result with or without twins indicates that there is indeed such an effect from education, and the other variables do not matter.