Roughly a century ago, many Swedes immigrated to America. They’ve done very well here. Only about 6.7 percent of Swedish-Americans live in poverty. Also a century ago, many Swedes decided to remain in Sweden. They’ve done well there, too. When two economists calculated Swedish poverty rates according to the American standard, they found that 6.7 percent of the Swedes in Sweden were living in poverty.

In other words, you had two groups with similar historical backgrounds living in entirely different political systems, and the poverty outcomes were the same.

A similar pattern applies to health care. In 1950, Swedes lived an average of 2.6 years longer than Americans. Over the next half-century, Sweden and the U.S. diverged politically. Sweden built a large welfare state with a national health service, while the U.S. did not. The result? There was basically no change in the life expectancy gap. Swedes now live 2.7 years longer.

Again, huge policy differences. Not huge outcome differences.

This is not to say that policy choices are meaningless. But we should be realistic about them. The influence of politics and policy is usually swamped by the influence of culture, ethnicity, psychology and a dozen other factors.

Which is precisely why one kind of policy — immigration policy — is so important. Minnesota is rather like Sweden. In contrast, New Mexico (state motto: "Thank God for Mississippi!") is still somewhat like Old Mexico, even after generations within the U.S. with relatively little additional immigration since the 1600s.

You can observe the same phenomenon when looking within the U.S. Last week, the American Human Development Project came out with its ”A Century Apart” survey of life in the United States. As you’d expect, ethnicity correlates to huge differences in how people live. Nationally, 50 percent of Asian-American adults have a college degree, compared with 31 percent of whites, 17 percent of African-Americans and 13 percent of Hispanics. Asian-Americans have a life expectancy of 87 years compared with 79 years for whites and 73 years for African-Americans.

Even in struggling parts of the country, Asian-Americans do well. In Michigan, for example, the Asian-American life expectancy is 90, while for the average white person it’s 79 and for the average African-American it’s 73. Income and education levels are also much higher.

The region you live in also makes a gigantic difference in how you will live. There are certain high-trust regions where highly educated people congregate, producing positive feedback loops of good culture and good human capital programs. This mostly happens in the northeastern states like New Jersey and Connecticut. There are other regions with low social trust, low education levels and negative feedback loops. This mostly happens in southern states like Arkansas and West Virginia.

I've written about trust a lot, and there's something quite peculiar about describing "New Jersey and Connecticut — i.e., Greater New York City — as a "high-trust region." I think New Yorkers would find that term insulting. Conversely, Arkansas and West Virginia are not precisely "low social trust." All else being equal, New Jerseyites tend to be lower in trust, in most senses of the word, than Arkansawyers. C'mon, New Jersey probably has more Sicilians than any other state. Sicilians were the classic representation in the social science literature (see Edward Banfield's study of Sicily, Moral Basis of a Backward Society) of "amoral familism."

But all else is not equal, especially the number of very bright, very motivated people who flock to the region to make and spend money.

Arkansas isn't Lake Wobegon or Provo when it comes to trust — in 1991 I once accidentally wandered up a deadend Ozark hollow while trying to get from Walmart headquarters to the Fayetteville airport and the locals sitting on their front porches looked at me like I might be a revenooer. On the other hand, Sam Walton built one of the most successful corporations in the world in Arkansas.

If you combine the influence of ethnicity and region, you get astounding lifestyle gaps. The average Asian-American in New Jersey lives an amazing 26 years longer and is 11 times more likely to have a graduate degree than the average American Indian in South Dakota. When you try to account for life outcome differences this gigantic, you find yourself beyond narrow economic incentives and in the murky world of social capital. What matters are historical experiences, cultural attitudes, child-rearing practices, family formation patterns, expectations about the future, work ethics and the quality of social bonds.

Sure, but, clearly, genetics also play some role in why the poor Sioux in South Dakota tend to drop dead young from alcoholism and diabetes. They didn't evolve with much alcohol or sugar around, and, hence, they have a hard time dealing with alcohol and sugar today. We ought to be sympathetic toward their genetic problems and look for ways to ameliorate them, not treat them as shamefully unspeakable.

Researchers have tried to disaggregate the influence of these soft factors and have found it nearly impossible. All we can say for sure is that different psychological, cultural and social factors combine in myriad ways to produce different viewpoints. As a result of these different viewpoints, the average behavior is different between different ethnic and geographic groups, leading to different life outcomes.

Oh, so that explains why Usain Bolt and all those other men of West African descent on three different continents have broken 10 seconds in the 100 meter dash so much more than the rest of the world combined: viewpoints! It's all in Usain's viewpoint. A more accurate way to phrase it is that researchers have made progress in disaggregating these soft factors, but the findings aren't very popular.

It is very hard for policy makers to use money to directly alter these viewpoints. In her book, ”What Money Can’t Buy,” Susan E. Mayer of the University of Chicago calculated what would happen if you could double the income of the poorest Americans. The results would be disappointingly small. Doubling parental income would barely reduce dropout rates of the children. It would have a small effect on reducing teen pregnancy. It would barely improve child outcomes overall.

So when we’re arguing about politics, we should be aware of how policy fits into the larger scheme of cultural and social influences. Bad policy can decimate the social fabric, but good policy can only modestly improve it.

But, all of the above suggests that immigration policy is the single most powerful policy tool, for good or bad. But when will Brooks ever follow out his logic and mention that?

Therefore, the first rule of policy-making should be, don’t promulgate a policy that will destroy social bonds. If you take tribes of people, exile them from their homelands and ship them to strange, arid lands, you’re going to produce bad outcomes for generations.

Is Brooks talking about the movie industry in arid Hollywood, CA? "Bad outcomes for generations" is an interesting way to characterize the totality of their output.

Oh, sorry, he seems to be talking about American Indians in South Dakota. My mistake.

Finally, we should all probably calm down about politics. Most of the proposals we argue about so ferociously will have only marginal effects on how we live, especially compared with the ethnic, regional and social differences that we so studiously ignore.

Except for immigration policy, right? That, according to this column's evidence and logic, should be the Big One. But only Angry, Evil People know anything the effects of immigration policy, so it must never be spoken of again.