"OK, Boomer." If you've heard this phrase from someone under 30, chances are you've said or done something that young person considers stupid or annoying, or both. And even if you haven't yet encountered the phrase, chances are you'll see it sometime soon, emblazoned on a t-shirt or hoodie worn by a member of Generation Z.

That's because dozens or maybe hundreds of enterprising teens and 20-somethings are selling everything from coffee mugs to shower curtains to mobile phone cases emblazoned with the slogan, which is their weary, eye-rolling response to the things their elders do and say. "A lot of them don't believe in climate change or don't believe people can get jobs with dyed hair, and a lot of them are stubborn in that view," 19-year-old Shannon O'Connor told the New York Times. "Teenagers just respond, 'OK, boomer.' It's like, we'll prove you wrong, we're still going to be successful because the world is changing."

O'Connor, at least, certainly seems to be proving her point. When she began selling t-shirts and hoodies with the phrase repeated seven times, followed by the tagline "Have A Terrible Day," orders began pouring in. At the time of her interview with the Times, she'd sold more than $10,000 worth; now that the story has run, I'm guessing it's at least twice that.

I wrote about how "ok boomer" has become Generation Z's default retort to old people on the internet and a rallying cry for millions of kids who are fed up with the status quo. https://t.co/xjVBZd4nlI -- Taylor Lorenz (@TaylorLorenz) October 29, 2019

O'Connor isn't the only one. Hundreds of OK Boomer products are for sale all over the web. Some young vendors told the Times that they plan to use the proceeds from their sales to help pay their college tuition or pay off their student loans, or for things that will help them survive.

Gen Z has a point.

Frankly, you can't blame teens and people in their 20s for being angry at older generations. The combined effects of out-of-control college tuition, out-of-control health care and health insurance costs, and out-of-control housing costs have combined to put the squeeze on younger generations, and Gen Z is truly disadvantaged by these economic forces.

And then there's climate change, an ongoing global disaster that has already cost many lives and driven even more people from their homes, and which could cost more than $1 trillion over the next few years, according to the public filings of 6,937 companies. People in their teens and 20s today rightly worry about what our planet will be like to live on 20 years from now when they're raising their own children. Some are worried enough about this that they've announced their intention to have no children at all unless somehow climate change is halted or reversed. Yet president Donald Trump, at 73 among the oldest Baby Boomers, has called climate change a concept "created by and for the Chinese in order to make U.S. manufacturing non-competitive."

Meantime, some Baby Boomers literally add insult to injury by calling Generation Z lazy, unable to focus on work, and addicted to technology. They've accused the younger cohort of being spoiled and unwilling to grow up, as in this clip that went viral on TikTok.