What if we tax plastic straws instead of ban them?

Rarely has a minor consumer product received more vilification than the plastic straw. As a symbol of human wastefulness and our careless disregard for the environment, straws are the near-perfect villain. You use a plastic straw once and toss it, but it stays with us forever, sitting in a landfill, floating in the sea or harming wildlife. That's why some local governments like that of New York City have stopped allowing them, along with other single-use plastics. This seems like a perfectly reasonable thing to do, even though plastic straws comprise only a small part of the total volume of plastic disposed of each year.

But eliminating plastic straws offers a case study in how simple solutions can be devilishly tricky to implement — and sometimes even worse than the problems they were meant to solve. For that, we can largely thank ourselves and our behavioral quirks. Let's look at just one example: Some restaurants and bars have replaced their plastic straws with reusable metal variants. But there's a hitch, as the New York Post recently reported: Customers keep taking the metal straws home with them.

This leaves restaurants holding the short straw, so to speak. Metal straws are expensive — perhaps a dollar apiece (or more) vs. a penny or two for the plastic version — and so replacement costs add up quickly.

This might not be so problematic if the metal straws that customers walk off with get reused frequently. But most probably go on display as novelties or sit forgotten in a utensil drawer. And this means the metal straws — which presumably required mining, plus large amounts of energy to convert into sheet metal and then fashion it into a cylindrical tube — don't provide the intended environmental benefit.

I'm not aware of any research on the relative environmental costs of producing different types of straws. But the evidence on reusable grocery bags is not heartening.

Reusable bags take much more energy than single-use paper or plastic bags to make. As a result they become an environmental plus only after a large number of uses — estimates suggest you need to use a reusable bag almost 40 times to break even in terms of environmental costs. Most reusable bags get lost, discarded or neglected in a closet before that milestone, undermining the case for them.

It would be surprising if the calculus for metal straws were any better. If metal straws get pilfered before they've been used enough, they may well be worse for the environment than their plastic peers.

So what's to be done? Economics offers a straightforward answer: Instead of banning single-use plastics, the right strategy is to tax them.

Taxes force people to pay — or in econ-speak, internalize — their own environmental costs. This tends to lead people to change their behavior: With plastic taxes, everyone reduces usage on the margin, with those who get relatively lower value from single-use plastics reducing their usage more. Even small taxes can change behavior substantially: A 7-cent tax on all grocery bags in Chicago, for example, was associated with a 42% drop in usage.

We can calibrate taxes to match actual estimates of environmental harm. This helps make environmental concerns tangible, and in particular makes people aware of which types of plastic are most harmful. Moreover, we can use the plastic tax revenue to support environmental causes, as Chicago and other cities have.

Of course, with these sorts of user and consumption taxes we have to be careful about inequality: The effective tax burden tends to fall more on those with lower incomes and/or those who need to use more plastic products. But tax-based policy can be designed to account for individual circumstances. For example, the high-end plastic bags in upscale grocery stores are often taxed more highly than bags at lower-cost stores. Meanwhile, some people have disabilities that mean they need to use straws; they could be exempted from the straw tax. Exempting these individuals from plastic straw bans would not help nearly as much, since under bans many restaurants will stop stocking plastic straws entirely.

So while it's true that reducing plastic straw usage might be an easy way to limit the harm we do to the environment, we need to make sure the limitations we place really are providing solutions. And that means taxes may be better than bans.

Scott Duke Kominers is a business and economics professor at Harvard University. He wrote this article for Bloomberg Opinion.