The plastic bags you use to carry your groceries are unsightly, wasteful, harmful to the environment and costly for the governments that have to haul them away. Or, they’re useful, necessary and the reason thousands of your fellow Americans have jobs.

Those are the core arguments of advocates and opponents of plastic bag taxes that have cropped up around the country in recent years. Environmentalists have pushed dozens of localities around the country to impose a surcharge on single-use grocery bags, in hopes of removing them from fragile ecosystems while making a buck or two in the process.

Now, Denver and New York City are considering their own fees. The Denver city council will vote on a proposal to charge 5 cents for each plastic bag consumers get from a grocery or convenience store. The New York city council is contemplating a bill, introduced in August, to charge 10 cents per bag, the highest tax in the nation. The proposals are similar to laws in Washington, Seattle, Maui and more than 30 localities around California that either charge for bags or ban them altogether.

“We see what other cities have done and how the fees have a huge impact in reducing the number of these bags that come into these communities and their waste streams,” said Denver city councilwoman Deborah Ortega, the prime sponsor of the bag tax. “We spend money dealing with plastic bags that damage the machines, that end up blowing all over the landfill.”

But do bag taxes have the intended consequences? The record is mixed.

Two years after Washington, D.C., started taxing plastic bags, their use had fallen by two-thirds, according to a study [pdf] conducted by the center-right Beacon Hill Institute at Suffolk University. Bag tax supporters frequently cite the decline in bag usage, and the attendant environmental benefits, as their main goals; the D.C. tax was billed as a way to clean up the Anacostia River.

After the initial decline, bag usage rises again, at least slightly, once consumers get used to the new cost. Studies showed plastic bag usage in Ireland, which began taxing single-use bags in 2002, rising after an initial free-fall. And it’s not clear that plastic bags themselves are responsible for a significant amount of litter anywhere.

“This is just another example of imposing a tax because it feels good to do so, as opposed to any kind of demonstrated benefit to society,” said David Tuerck, director of the Beacon Hill Institute. “The goals are always stated in sort of general terms about environmental impact and all, but there’s never any attempt to assess the cost.”

Reducing the number of plastic bags would benefit cities that spend millions to deposit them in landfills. New York City spends about $10 million every year sending 100,000 tons of plastic bags to landfills in three other states, according to the city’s deputy commissioner of sanitation. Denver grocery and convenience stores distribute about 130 million plastic bags per year, Ortega said.

There’s at least one group that benefits financially from bag taxes: The retailers who, until a tax is levied, have had to provide bags to customers for no charge. The Beacon Hill Institute study estimated that bag use would cost consumers $5.74 million in fiscal 2016. Washington’s city government takes 4 cents per bag, with retailers keeping the remaining penny; that means the government would take in an extra $4.6 million in 2016, while businesses would reap $1.15 million in additional revenue.

In California, where localities cannot levy a tax without state permission, cities that charge for plastic bags allow retailers to keep the entire amount. Those provisions, bag tax supporters say, win them buy-in from retailers who might otherwise be skeptical. New York City retailers would get to keep the 10 cents the tax backers want to impose.

“Retailers won’t [tax bags] by themselves, because then they look like the bad guy if they’re the only one on the block charging for a bag,” said Jennie R. Romer, founder of the Web site But with a charge, the retailers “no longer have to provide them for free. Once they get that, they’re generally okay with it.”

Denver expects to generate $1.7 million in plastic bag taxes during the first year a tax would be in effect.

The political fate of the two proposals is far from certain. Denver Mayor Michael Hancock has said he will veto the measure because even a nickel or a dime would add up to a burden on low-income families. Supporters of the New York proposal are still searching for votes.

States may be next to get in on the action. Six states — California, Massachusetts, New Jersey, Oregon, Rhode Island and Washington — considered statewide bans this year, according to the National Conference of State Legislatures. Eight states are considering fees or taxes on the bags.