Politics & Policy

Robert Putnam Distorts His Own Diversity Research

In last week’s column arguing against restricting immigration, David Brooks writes:

What about the rise of social distrust? Restrictionists often cite a 2007 Robert Putnam study finding that more diversity leads to less trust. But Putnam tells me they are distorting his research. He found that diversity’s benefits outweigh its disadvantages, that trust declines over the short term as places grow more diverse, but that over the long term Americans find new ways to boost social solidarity.

Putnam made the same “distortion” claim in a letter to the Wall Street Journal last year. It was just as disingenuous then as it is now. In fact, Putnam himself is the one distorting his research, by attempting to elevate his personal speculation (that diversity brings long-term net benefits) to the level of his data analysis (that shows diversity causes significant present-day problems).

To elaborate, the substance of Putnam’s 2007 paper is an analysis of his Social Capital Community Benchmark Survey. He shows that ethnic diversity is associated with reduced trust even after controlling for a long list of socioeconomic variables. The analysis is thorough and valuable, but it captures just one moment in time. It cannot tell us whether the effect on trust occurs only “over the short term,” or whether we will “find new ways to boost social solidarity.” Furthermore, Putnam never identifies positive effects of diversity from his own data — although an arguable exception is greater interest in politics — and he certainly never uses his data to address the question of whether “diversity’s benefits outweigh its disadvantages.” Indeed, Putnam’s data analysis section reads as a relentless, unsparing critique of diversity, with no promise of a long-run turnaround.

Uncomfortable with the implications of the data analysis, Putnam sandwiches it between misdirection and speculation. The misdirection comes at the beginning, in the form of a short list of reasons he believes ethnic diversity is a “valuable national asset.” Almost nothing on his list is about ethnic diversity per se. For example, immigrants do win Nobel Prizes and increase our GDP, but why diversity should get the credit is unclear. Also unclear is how these benefits are supposed to outweigh the negative consequences he uncovers in the data analysis. The speculation comes at the end, when Putnam offers his hope that U.S. Army integration, megachurches, and intermarriage among European ethnics are signs that the U.S. will eventually overcome the challenges of diversity. That’s it for the long-term — no hard evidence, just speculation.

Putnam is of course free to draw inferences and make predictions that go beyond his evidence, but it is inappropriate for him to insist that his own interpretation is inseparable from the data. Personally, I will continue to cite Putnam’s empirical findings without feeling compelled to cite the speculative musings with which he frames them.

Jason Richwine — Jason Richwine is a public-policy analyst and a contributor to National Review Online.

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