The amount of variety available at grocery stores is highly sensitive to income inequality, according to new research.

Even before COVID-19 and resulting shutdowns created gridlock for some global supply chains, the assortment at many neighborhood supermarkets was dwindling.  The cause was not a lack of supply, though, but rather a lack of demand created by a widening income gap in the US, the researchers report.

“We find that as we become a more unequal society, the total set of products we have to choose from is reduced, holding average level of income constant,” says Raphael Thomadsen, professor of marketing at the Olin Business School at Washington University in St. Louis.

“This happens largely because as income inequality grows, the people whose income is growing do not spend much more at supermarkets. But people whose incomes are cut reduce their spending quite a bit, leaving less total spending and, thus, less support for niche products.”

The researchers looked at the level of income distribution disparity in more than 1,700 US counties between 2007 and 2013, using the Gini income index. A Gini index of zero expresses absolute equality, where everyone has the same income. An index of 1 represents maximum inequality.

Then they overlaid that with a look at the product range available in grocery stores within each county across nearly 950 categories of non-perishable household items.

Consumer packaged goods manufacturers consistently supplied many new products over the time of the study. More than two-thirds of the counties had a widening of income inequality. In those counties—and at individual stores in those counties—the available assortment of products tended to grow 18% slower than in the counties where income inequality narrowed.

Read the full article about the impact of income inequality on grocery store selections by Sara Savat at Futurity.