A funny thing started to happen about 15 years ago. Maybe you noticed it only when you went to take a new shirt out of its maiden voyage in the washer and discovered the hem had unraveled. Or maybe the lifetime of your jeans began to shorten perceptibly. First, you found yourself at the store for a replacement pair, a bit sooner than you might have expected. Then you were there again less than a year later. Then you’re there with the new pair ripped across the knees, less than 2 months after you bought them, embarrassed but also confused. Are you imagining it, or was this different before?

I remember acutely the moment in 2010 when I put on a pair of what looked like black brogues and discovered they were nothing but a kind of vinyl sac with a rubber pad for a sole. They aren’t shoes, I realized with a chill, looking around the sleek glass box of a Manhattan store. They just look like them. And no wonder. For $20 you can’t buy shoes, not really. You’re buying a facsimile designed to get you out the door and back again in a couple of weeks, when brogues are out of style and ballet flats are in. You aren’t imagining it: clothes have changed, and what has happened is a whodunit where the stakes are very, very high.

In the 1950s, Americans spent a whopping ten percent of their income on clothes. These garments were relatively expensive, compared to what we expect now, but they also lasted longer. When people had to choose a new skirt or suit for the office, they might not be able to afford another one for quite some time. In fact, as journalist Elizabeth Cline wrote in her 2012 book Overdressed: The Shockingly High Cost of Cheap Fashion, for much of the twentieth century, many people often did not buy clothes more than a few times a year. Even until relatively recently—as late as the 1980s—new clothes were usually occasional purchases. Labor has always been the most expensive part of clothing, and an irreducible one at that: It is actually impossible to mechanize a seamstress, beyond giving her a sewing machine. “Because clothing is so labor-intensive, the price of labor directly affects the retail price of clothes,” says Cline, who has continued to cover the social and environmental impact of modern fashion.

However, in 1993 came a turning point. With the passage of the North American Free Trade Agreement (NAFTA), it became much, much easier to import clothing. Over the next ten or so years, a quota system that had limited the number of imported items entering the US was abolished. Very swiftly, US-based textile mills and factories went out of business. Around the world, similar events happened in developed countries with free-trade agreements. Labor, that limiting factor, was at least ten or 20 times cheaper in other places. Companies that didn’t move their operations out of the US could not compete. Not long afterward, one of the most successful business models of this century took advantage of this change to shoulder its way to the front of the pack: it is now called “fast fashion.”

Fast-fashion companies such as Zara and H&M make their money by shortening the time between trends and encouraging customers to buy inexpensive clothes that, in many cases, appear to be made to last no longer than the lifetime of the fad. Currently, H&M alone makes between 550 and 600 million items of clothing a year. And thanks to the fact that most clothes today are made by people working for low wages, developed-world consumers have never spent so little on their wardrobes. It might surprise you to learn that Americans now buy at least one item of clothing a week.

Run this clock forward over the years, however, and you start to see a problem (beyond the humanitarian one—companies continue to use factories like the one in which more than 1,000 workers died in a building collapse in Bangladesh in 2013). Already, says Cline, “global clothing consumption has doubled in the past 15 years.” The industry, driven by fast fashion, has steadily become one of the most serious polluters in the world. Clothing manufacture was never exactly tidy, what with toxic dyes, copious amounts of water needed for growing fiber and processing fabrics, and waste from factories. But in 2015, carbon emissions from clothes surpassed those emitted from all international flights and all maritime shipping combined. Cotton, for example, uses more pesticides than any other crop—and organic cotton takes up more land and much more water than conventionally grown cotton. At the same time, clothes are worn for less time than they ever have been previously. Every year, 12.7 million tons of textiles enter American landfills; in 2015 in the UK, 300,000 tons of clothes went in, about ten pounds per person. Giving old clothes to charity isn’t the charitable act you might think it is—many of the clothes made today are of such poor quality that they cannot be sold again.

You might not think of yourself as the kind of person who cares much about clothes. I know I didn’t. As someone who has always felt like a brain inconveniently hampered by a body, I can’t say I ever thought much about them—except to wonder why, as an averagely shaped human being, I found it so hard to find things that fit. But even if you don’t spend much time thinking about fashion, this concerns you.