Facts Do Not Speak For Themselves

In a recent online exchange, one poster claimed that Democrats were obviously better than Republicans, since blue states had a higher average income and a more educated population than red states. Another responded that it was the other way around, red states were better, since on net people were moving from blue states to red states, voting with their feet.

Both factual claims could be, I think are, true. Neither implies its conclusion.

Start with the first. Median household income in states controlled by Republicans is about $60,000, in states controlled by Democrats about $72,000.¹ The poverty rate, several measures of educational outcome, the uninsured rate and GDP per capita all look better in the blue states. Only the unemployment rate is better, lower, in the red states. That looks like evidence that it is better for a state’s inhabitants to have a Democratic governor and legislature.

To see why it is not very good evidence, think about alternative explanations for the pattern. One might be that red states are more attractive places for poor people to live in. California, where I live, has a statewide minimum wage of $16.50, city minimum wages as high as $19.90, a fast food minimum wage of $20. Texas has the federal minimum wage of $7.25. A high minimum wage means that workers who are not worth that much to any employer do not have jobs, gives employers an incentive to substitute skilled workers and machinery for unskilled workers. Given the politics around the issue I expect blue states to mostly have higher minimum wage rates than red states and that fits a casual look at the data. If more poor people choose to live in red states that would explain all of the observed comparisons, would not imply that a poor person could raise his income by moving to a blue state or that a rich person would lower his by moving to a red state.

I will leave it to readers, especially Republicans, to think of more possible explanations for the pattern other than Democratic policies making people richer and better educated.

What about the argument the other way, people voting with their feet? One problem with that argument is that red states might be attractive for reasons other than that they are red. Many red states are in the warm south, most blue states in the cold north; there could be reasons having nothing to do with politics for people to want to move from colder to warmer places.

A second problem with the argument is that immigration flows are evidence not of how many people want to live where but of how the number has changed. If last year 60% of the population preferred blue states, this year 59%, there would be a net flow to red states even though most people still preferred blue.

There is one more problem with both arguments — they treat the politics of a state as a given, cause rather than effect. It might be the other way around. Perhaps richer people are more inclined to vote for Democrats, poorer for Republicans. A Democrat might take that as evidence that Democrats are better, as revealed by the preferences of richer and, on average, better educated people. A Republican might take it as evidence that rich people don’t want poor neighbors so support policies such as high minimum wages to push them out.

I have started with this particular issue in part because I saw arguments on both sides, in part because it started me thinking of the problem in reasoning from facts to conclusions, but the issue arises in lots of other controversies and questions.

Here are a few.

Exercise and the Heart

A few years ago my then cardiologist, who had been urging me to get more exercise, mentioned that he was one of the authors of a published article showing that regular exercise reduced the risk of a heart attack. Being curious, I read it. The article’s measure of exercise, how much exercise people said they got, did indeed correlate with a lower rate of heart attacks, but there was no way of telling from their data whether exercise made heart attacks less likely or people in better health, hence less likely to have heart attacks, were more inclined to exercise. If I had been a referee for the paper I would have taken the failure to even mention that problem, the problem of the direction of causality, as a reason to reject the article.

Viagra as the Cure for Alzheimer’s

A few years ago, news stories reported evidence that taking Viagra reduced the risk of Alzheimer’s. That was good news for aging men but unfortunately further research did not support the conclusion. The study got its information on who used Viagra from insurance company data. The correlation they found might be due to Viagra reducing the chance of Alzheimer’s but might also be due to men slipping towards Alzheimer’s being less sexually active, hence less likely to want Viagra.

Salt and Mortality

Is salt good or bad for you? From the Center for Disease Control we have:

Eating too much sodium can increase your blood pressure and your risk for heart disease and stroke. Together, heart disease and stroke kill more Americans each year than any other cause.

… Most people eat too much sodium (“About Sodium and Health”)

But from the National Institute of Health:

Conclusion: Our observation of sodium intake correlating positively with life expectancy and inversely with all-cause mortality worldwide and in high-income countries argues against dietary sodium intake being a culprit of curtailing life span or a risk factor for premature death. (“Sodium intake, life expectancy, and all-cause mortality,” NIH)

If both factual claims are true, as I think they probably are, the implication is that the increased risk from heart disease and stroke is more than balanced by the decreased risk from other causes of death. If so, the CDC fact is true, its conclusion false.

The pattern of a negative effect outweighed by a positive effect is not merely possible but, in the biological context, something we should be looking for. We are, after all, very sophisticated biological machines designed by evolution. If more salt is bad for us there ought to have been selective pressure for a tendency to absorb up to the optimal level, excrete the surplus.

We are not perfectly optimized against our present environment, if only because some features of that environment are too recent for humans, with their long generations, to have adapted to yet; perhaps the environment we evolved in did not contain sufficient sources of salt to raise a risk of consuming too much of it. But the fact that a change that evolution could have made benefits us in one way is a reason to at least suspect that it harms us in another.

The same logic applies to things optimized by humans. If a change in some product would be an obvious improvement in some ways it is probably a worsening in others. Here again there may be exceptions, failures in human design, improvements the producer missed. But that should not be the first guess.

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1. My source, for this and the other comparisons, is “The Growing Divide: Red States vs. Blue States.” Income figures are for 2018; the income difference has existed since about 2007. The author defines a state as blue if Democrats control both houses of the legislature and the governor’s office, red similarly.