5 ms·

There is extensive literature on twin studies that finds effects of roughly this magnitude on a range of health/earnings/educational metrics. 40%-50% genes 40%-

There is extensive literature on twin studies that finds effects of roughly this magnitude on a range of health/earnings/educational metrics. 40%-50% genes 40%-50% random/non-shared environments and small impact of shared environment. https://www.researchgate.net/profile/Bruce_Sacerdote/publication/228389297_Nature_and_Nurture_Effects_on_Children%27s_Outcomes_What_Have_We_Learned_from_Studies_of_Twins_and_Adoptees/links/55b62f1808ae9289a08aabb3.pdf https://www.researchgate.net/profile/Bruce_Sacerdote/publica...

eloff 7y ago
Also IQ seems structured this way, but even more heritable and almost nothing to do with shared environment. Incidentally IQ is also strongly correlated with lifetime earnings. In fact if you can know only one thing about a job candidate, it's the measure you should pick.
- NateEag 7y ago
  A candidate that will earn a lot of money is not what you're looking for when hiring. You want someone who will do the work well and will help the company succeed. Indeed, you could argue that a high earner is, all else being equal, something you should avoid selecting as a hiring manager.
  - jdavis703 7y ago
    This means the manager needs to correctly align employee incentives. For example pay sales people a commission or give employees shares. This is business school 101.
    - NateEag 7y ago
      I do not believe a person's salary history gives you any useful information about their effectiveness as an employee. I have worked with people who had higher salaries than I did who were clearly much worse at the job (a backend architect at a past gig told me that UTF-8 supported only 256 characters, and refused to acknowledge it when I pointed out sources that showed he was wrong).
  - krageon 7y ago
    Am I correct in reading this as you making the claim that your salary is not directly (or even at all) commensurate with your contribution to the company?
    - JoeAltmaier 7y ago
      The claim was only that hiring by previous income is not commensurate with contribution at the new job.
  - eloff 7y ago
    Sorry, I see how that can be confusing that I switched topics like that. I mean IQ is the best single measure predictor of success on the job. It's also strongly correlated with lifetime earnings. And it should surprise nobody that success on the job and lifetime earnings are very tightly coupled.
- Symmetry 7y ago
  It has almost nothing to do with shared environment in the wealthy first world countries we study this in. But malnutrition, disease, and other factors can certainly have large effects. The introduction of iodized salt in the US raised IQs by 10 points in certain areas where people's diets and water were sufficiently iodine-deficient.
  - JoeAltmaier 7y ago
    And the 'free lunch program' raised public health/reduced malnutrition by a large factor when introduced in the US. Urban legend has it that the military mandated it because of poor WWII conscript health, but free lunch predated that by 50 years. It was a federal act only after WWII because of scarcity and the decline of local programs.
  - eloff 7y ago
    Yes, that's an excellent point. The socioeconomic status of your parents is a big influence up to a point. In developed counties we don't see this effect as much because it's the baseline. Almost everybody gets sufficient nutrition and medical care to meet the very low standards where it would otherwise negatively affect your intelligence and development.
evrydayhustling 7y ago
So, they do this by comparing correlations in MZ (genetically identical) and DZ (typical sibling genetics) twin outcomes. Doesn't that assume that the fact of being DZ vs MZ does not itself create environmental (non-genetic) effects? The identical twins I know face particular social pressures to respond to their twin identity, which could drive towards outcomes that are more correlated -- or not! But it seems weird to base a branch of literature on the assumption that it's not. Is this addressed?
- tomp 7y ago
  You can also compare identical twins that grow up in the same family, vs. identical twins that were separated at birth... although I imagine you wouldn't have a lot of samples.
- Symmetry 7y ago
  That's a reasonable sort of question but would you say that MZ twins are treated differently enough to explain 40% of variation in earnings? If they were all locked in cellars out of shame I could see that being the case but that doesn't square with the identical twins I've known. But it actually is addressed by other studies such as adoption studies that show generally the same results. And, of course, there are potential problems with adoption studies too. But wouldn't it be suspicious if every[1] method of studying the problem we tried gives fairly close numbers but only because they all happen to be biased by the same amount in the same direction? [1]GWASes give lower numbers but we know that there are many sorts of genetic interaction they don't cover so this is expected.
- barry-cotter 7y ago
  This is an empirical question and as far as we can tell if there’s pressure to be more similar or more different it washes out. Identical twins reared together are no more similar than ones raised apart on a huge host of traits.
- oli5679 7y ago
  Yes that is valid point about the limitation of this approach. There are 3 methods to address it, none of them are perfect: (1) Statistically compare the population of twins vs the population of non-twins. The paper I linked to has more specifics on this, but twins earn similar amounts of money, live similar lengths of time, do similarly well in exams vs. non-twins, so it any twin-specific genetic effect has to simultaneously be strong enough to cause this discrepancy, but not strong enough to impact population means. (2) Compare adoptees to genetic offspring of parents. This has the same issue that you pointed out (maybe there is something specific about adoptees) but the two together find roughly similar effect magnitudes, which reenforce each-other. I'm actually a bit more concerned about adoption being less 'clean' an identification strategy than twin studies, because it's a complicated social process. (3) Look at genetic variation at population level and find genetic markers that explain variation, using Mendelian randomization as identification strategy - this is technically very challenging, and has only recently become feasible. So far research have only been able to explain around 7% of IQ for example with specific genetic markers, but it will be interesting to see if this creeps up as the field matures. The big puzzle here is the large variation that we between cultures - moving time-periods, or countries can significantly change your life-expectancy, earnings, test-scores or even IQ. I don't know how to reconcile this with the strange finding of this research strand is that family level environmental effects (shared environment) seem to be much less important than the conventional wisdom would suggest. Links https://www.sciencedirect.com/science/article/pii/B0080427073001759 https://www.sciencedirect.com/science/article/pii/B008042707... (gated) https://en.wikipedia.org/wiki/Mendelian_randomization https://en.wikipedia.org/wiki/Mendelian_randomization https://www.newscientist.com/article/2163484-found-more-than-500-genes-that-are-linked-to-intelligence/ https://www.newscientist.com/article/2163484-found-more-than... https://en.wikipedia.org/wiki/Flynn_effect https://en.wikipedia.org/wiki/Flynn_effect

eloff 7y ago

Also IQ seems structured this way, but even more heritable and almost nothing to do with shared environment. Incidentally IQ is also strongly correlated with lifetime earnings. In fact if you can know only one thing about a job candidate, it's the measure you should pick.

NateEag 7y ago
A candidate that will earn a lot of money is not what you're looking for when hiring. You want someone who will do the work well and will help the company succeed. Indeed, you could argue that a high earner is, all else being equal, something you should avoid selecting as a hiring manager.
- jdavis703 7y ago
  This means the manager needs to correctly align employee incentives. For example pay sales people a commission or give employees shares. This is business school 101.
  - NateEag 7y ago
    I do not believe a person's salary history gives you any useful information about their effectiveness as an employee. I have worked with people who had higher salaries than I did who were clearly much worse at the job (a backend architect at a past gig told me that UTF-8 supported only 256 characters, and refused to acknowledge it when I pointed out sources that showed he was wrong).
- krageon 7y ago
  Am I correct in reading this as you making the claim that your salary is not directly (or even at all) commensurate with your contribution to the company?
  - JoeAltmaier 7y ago
    The claim was only that hiring by previous income is not commensurate with contribution at the new job.
- eloff 7y ago
  Sorry, I see how that can be confusing that I switched topics like that. I mean IQ is the best single measure predictor of success on the job. It's also strongly correlated with lifetime earnings. And it should surprise nobody that success on the job and lifetime earnings are very tightly coupled.
Symmetry 7y ago
It has almost nothing to do with shared environment in the wealthy first world countries we study this in. But malnutrition, disease, and other factors can certainly have large effects. The introduction of iodized salt in the US raised IQs by 10 points in certain areas where people's diets and water were sufficiently iodine-deficient.
- JoeAltmaier 7y ago
  And the 'free lunch program' raised public health/reduced malnutrition by a large factor when introduced in the US. Urban legend has it that the military mandated it because of poor WWII conscript health, but free lunch predated that by 50 years. It was a federal act only after WWII because of scarcity and the decline of local programs.
- eloff 7y ago
  Yes, that's an excellent point. The socioeconomic status of your parents is a big influence up to a point. In developed counties we don't see this effect as much because it's the baseline. Almost everybody gets sufficient nutrition and medical care to meet the very low standards where it would otherwise negatively affect your intelligence and development.

evrydayhustling 7y ago

So, they do this by comparing correlations in MZ (genetically identical) and DZ (typical sibling genetics) twin outcomes. Doesn't that assume that the fact of being DZ vs MZ does not itself create environmental (non-genetic) effects? The identical twins I know face particular social pressures to respond to their twin identity, which could drive towards outcomes that are more correlated -- or not! But it seems weird to base a branch of literature on the assumption that it's not. Is this addressed?

tomp 7y ago
You can also compare identical twins that grow up in the same family, vs. identical twins that were separated at birth... although I imagine you wouldn't have a lot of samples.
Symmetry 7y ago
That's a reasonable sort of question but would you say that MZ twins are treated differently enough to explain 40% of variation in earnings? If they were all locked in cellars out of shame I could see that being the case but that doesn't square with the identical twins I've known. But it actually is addressed by other studies such as adoption studies that show generally the same results. And, of course, there are potential problems with adoption studies too. But wouldn't it be suspicious if every[1] method of studying the problem we tried gives fairly close numbers but only because they all happen to be biased by the same amount in the same direction? [1]GWASes give lower numbers but we know that there are many sorts of genetic interaction they don't cover so this is expected.
barry-cotter 7y ago
This is an empirical question and as far as we can tell if there’s pressure to be more similar or more different it washes out. Identical twins reared together are no more similar than ones raised apart on a huge host of traits.
oli5679 7y ago
Yes that is valid point about the limitation of this approach. There are 3 methods to address it, none of them are perfect: (1) Statistically compare the population of twins vs the population of non-twins. The paper I linked to has more specifics on this, but twins earn similar amounts of money, live similar lengths of time, do similarly well in exams vs. non-twins, so it any twin-specific genetic effect has to simultaneously be strong enough to cause this discrepancy, but not strong enough to impact population means. (2) Compare adoptees to genetic offspring of parents. This has the same issue that you pointed out (maybe there is something specific about adoptees) but the two together find roughly similar effect magnitudes, which reenforce each-other. I'm actually a bit more concerned about adoption being less 'clean' an identification strategy than twin studies, because it's a complicated social process. (3) Look at genetic variation at population level and find genetic markers that explain variation, using Mendelian randomization as identification strategy - this is technically very challenging, and has only recently become feasible. So far research have only been able to explain around 7% of IQ for example with specific genetic markers, but it will be interesting to see if this creeps up as the field matures. The big puzzle here is the large variation that we between cultures - moving time-periods, or countries can significantly change your life-expectancy, earnings, test-scores or even IQ. I don't know how to reconcile this with the strange finding of this research strand is that family level environmental effects (shared environment) seem to be much less important than the conventional wisdom would suggest. Links https://www.sciencedirect.com/science/article/pii/B0080427073001759 https://www.sciencedirect.com/science/article/pii/B008042707... (gated) https://en.wikipedia.org/wiki/Mendelian_randomization https://en.wikipedia.org/wiki/Mendelian_randomization https://www.newscientist.com/article/2163484-found-more-than-500-genes-that-are-linked-to-intelligence/ https://www.newscientist.com/article/2163484-found-more-than... https://en.wikipedia.org/wiki/Flynn_effect https://en.wikipedia.org/wiki/Flynn_effect