Emily Badger:

Using panel data on more than 100,000 American households over seven years, they tracked purchases of toilet paper, which has the great benefit of being non-perishable and steadily consumed (it’s hard to go without, but we also don’t use more just because we happen to have more in the house). That’s nearly 3 million toilet paper purchases.

When Orhun and Palazzolo compared households with similar consumption rates shopping at comparable stores — and controlling for two-ply TP — they found that the poor were less likely than wealthier households to buy bigger packages, or to time their purchases to take advantage of sales. By failing to do so, they paid about 5.9 percent more per sheet of toilet paper — a little less than what they saved by buying cheaper brands in the first place (8.8 percent).

Perhaps this sounds like a subtle discovery about minor household goods. But it supports a larger point about poverty: It’s expensive to be poor. Or, to state the same from another angle: Having more money gives people the luxury of paying less for things.

In the case of toilet paper, or any number of other storable goods like canned tomatoes, rice or paper towels, shoppers have to pay more up front to reap savings over time. And the poor often can’t afford to do that — to pay $24 for a 30-pack instead of $5 for a four-pack. Then, because they can’t stock up, they can’t afford to wait until the next sale comes around. When the toilet paper runs out, they have to run to the store for another small quantity of it — whatever it costs in that moment. Because they can’t use one money-saving strategy, they can’t use the other, either.

The use of connected math has not helped. More, here.