Meet Jim Manzi and the art of randomized field trials.
Uncontrolled: The Surprising Payoff of Trial-and-Error
for Business, Politics, and Society
By Jim Manzi
(Basic Books, 320 pages, $28.99)
THE FIRST THING Barack Obama did as president was enact the stimulus. Two of his economic advisers, Christina Romer and Jared Bernstein, preceded the rollout of the $800 billion bill with a now infamous prediction that it would prevent unemployment from climbing above 8 percent.
Three-plus years later, the unemployment rate hasn’t fallen below 8 percent (as of this writing), and Romer and Bernstein are a cautionary tale about the perils of making predictions.
Yet, while the public mostly thinks of the stimulus as a self-evident failure, its authors are unconvinced. If anything, they think it should have been bigger. Almost no one who had a strong opinion about the wisdom of stimulus before 2009 has changed his mind since.
As the administration argues, it’s quite possible that unemployment is still sky-high not because the stimulus failed, but because the economy was in even worse shape than was thought at the time of the Romer-Bernstein prediction. If the stimulus hadn’t been enacted, unemployment might even be worse than it is today.
In other words, there’s no way to assess the stimulus without knowing the counterfactual of what would have happened if the stimulus had never passed. The question is: Without knowing what would have happened in the world in which the stimulus never passed, could even the most sophisticated study provide a definitive estimate of its impact?
Jim Manzi, author of Uncontrolled, believes the answer is no: The question of whether the stimulus worked simply cannot be answered with the available evidence. To the extent that social scientists rely on studies like those justifying or discrediting the stimulus, they are fundamentally practicing an art, not a science.
Through his work as a software consultant, Manzi, who’s also associated with the Manhattan Institute and National Review, has become convinced that a type of study known as randomized field trials (RFTs) can do what other models cannot, in politics as well as business: generate reliable predictions.
What is a randomized field trial? It is essentially a clinical trial, or what most people would think of as the backbone of hard science and medicine. For example, to test a drug’s effectiveness, a researcher would give a dose of the drug to a treatment group in a randomly selected sample and placebos to a control group. By measuring the difference between the two groups afterward, the researcher obtains evidence that doctors and patients can trust.
Even simpler, think of kindergartners watering only half of a flower bed. When the other half withers in a day or so, the kids have absolute confi dence that water helps plants.
RFTs essentially bring the same approach to different areas. Although in some ways they are simpler than many prevailing statistical methods, Manzi argues persuasively that they could drastically improve the way governments operate.
The problem that RFTs address lies in what Manzi calls “causal density.” The factors affecting the outcome of any one intervention are just too numerous to control for them in a normal study.
Manzi gives an example from business to illustrate the concept of causal density. A company that owned thousands of convenience stores named QwikMart and FastMart asked Manzi to determine whether renaming all the QwikMarts “FastMart” would increase sales (the average FastMart had higher sales).
Although that sounds like an easy question, it proves quite diffi cult to answer reliably. Manzi points out that any number of factors—he goes through 32 before warning that the list could go on forever—could also affect sales, meaning that anyone trying to separate the impact of the name “FastMart” from all the other factors would fi nd doing so extremely difficult. Furthermore, each and every factor affects all the others, creating infi - nite interactions that any study would also have to control for.
For example, it’s possible that the presence of an ATM in a store increases sales, rather than the name “FastMart.” But Manzi cautions that to know for sure, one would also have to control for whether or not the ATM is, for instance, in a small or large store (it’s conceivable that ATMs in small stores Could lead to crowding and reduce sales). Furthermore, one would have to take into account higherorder interactions, such as whether or not a FastMart that has an ATM and is large is along a highway, in which case it’s probably so crowded that an ATM hurts sales even if it’s a large store.
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