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It was only about 40 years ago that plastic bags became standard at U.S. grocery stores. This also made them standard in sewers, landfills, rivers and the Great Pacific Garbage Patch. They clog drains and cause floods, litter landscapes and kill wildlife. The national movement to get rid of them is gaining steam — with more than 240 cities and counties passing laws that ban or tax them since 2007. New York recently became the second U.S. state to ban them. But these bans may be hurting the environment more than helping it.

University of Sydney economist Rebecca Taylor started studying bag regulations because it seemed as though every time she moved for a new job — from Washington, D.C., to California to Australia — bag restrictions were implemented shortly after. “Yeah, these policies might be following me,” she jokes. Taylor recently published a study of bag regulations in California. It’s a classic tale of unintended consequences.

Paper or plastic?

Before California banned plastic shopping bags statewide in late 2016, a wave of 139 California cities and counties implemented the policy themselves. Taylor and colleagues compared bag use in cities with bans with those without them. For six months, they spent weekends in grocery stores tallying the types of bags people carried out (she admits these weren’t her wildest weekends). She also analyzed these stores’ sales data.

Taylor found these bag bans did what they were supposed to: People in the cities with the bans used fewer plastic bags, which led to about 40 million fewer pounds of plastic trash per year. But people who used to reuse their shopping bags for other purposes, like picking up dog poop or lining trash bins, still needed bags. “What I found was that sales of garbage bags actually skyrocketed after plastic grocery bags were banned,” she says. This was particularly the case for small, 4-gallon bags, which saw a 120 percent increase in sales after bans went into effect.

Are Plastic Bag Bans Garbage?

Chart: Koko Nakajima and Alyson Hurt/NPR