Class and IQ:

The NYT and the WSJ have been writing about the lack of change in class status, but Mickey Kaus wonders if they'll mention IQ:

The NYT's Intelligence Test: The big question about the New York Times' Big Deal "Class Matters" series is how it will treat the role of genetically inherited traits--including but not limited to "intelligence"--in reducing mobility and perpetuating an aristocracy of the successful. Let's hope they do better than the WSJ's David Wessel, who blew off the genetic vector in a single unsatisfactory, buried paragraph:

Why aren't the escalators working better? Figuring out how parents pass along economic status, apart from the obvious but limited factor of financial bequests, is tough. But education appears to play an important role. In contrast to the 1970s, a college diploma is increasingly valuable in today's job market. The tendency of college grads to marry other college grads and send their children to better elementary and high schools and on to college gives their children a lasting edge.

The notion that the offspring of smart, successful people are also smart and successful is appealing, and there is a link between parent and child IQ scores. But most research finds IQ isn't a very big factor in predicting economic success. [Emph. added]

The r-squared of IQ and income is around 10% and it's a common error to think that's not a "very big factor." The problem with this line of thought is that Life Is Very Complicated, which means that a huge number of factors contribute to determining income. Relative to the multitudinous other factors, IQ plays a sizable role, so that the average income difference between people with IQs of 115 and 85, say, is very large. Here, for example, is Charles Murray describing his study of 710 pairs of American siblings for the Times of London:

"Each pair consists of one sibling with an IQ in the normal range of 90-110, a range that includes 50% of the population. I will call this group the normals. The second sibling in each pair had an IQ either higher than 110, putting him in the top quartile of intelligence (the brights) or lower than 90, putting him in the bottom quartile (the dulls). These constraints produced a sample of 710 pairs. How much difference did IQ make? Earned income is a good place to begin. In 1993, when we took our most recent look at them, members of the sample were aged 28-36. That year, the bright siblings earned almost double the average of the dull: £22,400 compared to £11,800. The normals were in the middle, averaging £16,800." [IQ Will Put You In Your Place, Charles Murray, Sunday Times, UK, Day 25, 1997]

The Washington Monthly's blogger Kevin Drum takes a stance similar to Mickey's:

Ever since World War II, the United States has done a phenomenal job of sorting people by talent. Not a perfect job, but an astonishingly good one nonetheless. All four of my grandparents, for example, would almost certainly have gone to college if they had turned 18 in the 1960s, but that just wasn't in the cards for any of them a century ago. Today, though, as a matter of deliberate policy, the vast majority of people who have the talent to succeed in college get the chance to try. As a result, they moved upward into the middle and upper classes decades ago, and their children have followed them.

But there's only a moderate amount of sorting left to be done. Random chance, both in nature and nurture, will always play a role in life outcomes, but that role has gotten smaller and smaller as the sorting has progressed. The result is that life roles have become more hardened. While incomes of the well-off have skyrocketed over the past 30 years, working and middle class incomes have stagnated. At the same time, the incomes — and jobs — they do have are far more unstable than they were a few decades ago. And as recent research indicates, most of them are increasingly stuck in these grim circumstances: every decade, fewer and fewer of them — and fewer and fewer of their children — have any realistic chance of moving up the income ladder.

This makes a lot of sense, but I want to urge caution: There's still a lot of IQ variation found between siblings raised in the same home. I haven't done the math necessary to figure out how much impact assortative mating would have had by now.

My published articles are archived at iSteve.com -- Steve Sailer