We know that living in a poor community makes you less likely to live a long life. New evidence suggests that living in a community with high income inequality also seems to be bad for your health.
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A study from researchers at the University of Wisconsin Population Health Institute examined a series of risk factors that help explain the health (or sickness) of counties in the United States. In addition to the suspects you might expect — a high smoking rate, a lot of violent crime — the researchers found that people in unequal communities were more likely to die before the age of 75 than people in more equal communities, even if the average incomes were the same.
“It’s not just the level of income in a community that matters — it’s also how income is distributed,” said Bridget Catlin, the co-director of the project, called the County Health Rankings and Roadmaps.
Many factors besides inequality affect health, of course. How much people smoke, whether they are obese, and the safety of air and water, among many other factors, make a difference. But the effect of inequality was statistically significant, equivalent to a difference of about 11 days of life between high- and low-inequality places. The differences were small, but for every increment that a community became more unequal, the proportion of residents dying before the age of 75 went up.
The research on inequality at the county level is new, but existing literature suggests there are relationships between income inequality and life expectancy among countries in the world. “Inequality effects, over and above average income, are pretty well established,” said S.V. Subramanian, a professor of population health and geography at Harvard, who has studied the phenomenon. We know that inequality tends to concentrate income in fewer hands, creating more low-income households — and people in low-income households don’t live as long. But what causes the drop in life expectancy is debatable.
One theory is that while money does tend to buy better health, it makes a bigger difference for people low on the income scale than those at the top. That means that having fewer very poor people in a community will improve average health more than having fewer very rich people will diminish it.
But another, more sociological theory, has to do with the communities themselves. The researchers think that places where wealthy residents can essentially buy their way out of social services may have less cohesion and investment in things like education and public health that we know affect life span. There is also literature suggesting that it’s stressful to live among people who are wealthier than you. That stress may translate into mental health problems or cardiac disease for lower-income residents of unequal places.
The researchers measured inequality by comparing the incomes of people in a given place who earned the 80th percentile in the county with the incomes of those in 20th percentile. Then they measured life expectancy using a custom measurement they developed — it counts the “potential life years lost” in each community by measuring all those who died before the age of 75, and the age at which they died. So someone who died at age 70 would have five years of potential life lost. Then they adjusted the numbers according to how old people were in the county, so counties with more old people wouldn’t look sicker than counties that were younger. The study looked at only the average life span and not that of higher-income versus lower-income residents.
For every one-point increase in the ratio between high and low earners in a county, there were about five years lost for every 1,000 people. That’s about the same difference they observed when a community’s smoking rate increased by 4 percent or its obesity rate rose by 3 percent. Researchers said that inequality effect persisted even when they compared communities of similar average income and racial composition.
Here’s what that means in some real counties. The researchers compared the adjoining Park and Fremont Counties in Wyoming. Both have relatively small populations and are predominantly white. Both include parts of large national parks. But the Fremont inequality ratio is 4.6, compared with Park’s 3.6. And, in Fremont County, there are 13 years of potential life lost for every 1,000 residents, compared with only 7.5 in Park.