About every 20 years, the comic book industry faces its end. The last time was in the late ’90s, so here we go again. A few weeks ago, Diamond Comic Distributors Inc. — which has a virtual monopoly on distributing comic books in North America — announced it would stop distributing to retailers all material scheduled for April and beyond. All thanks to the COVID-19 crisis. Recently it began furloughing employees, which is another bad sign.

But worse, if Diamond wasn’t ready for this, imagine how the shutdown is affecting local mom-and-pop comic book shops. Many stores run on very narrow profit margins. Circumstances are truly dire. But then again, they have been before.

Back in the late 1940s and early ‘50s, comic books were selling 80 million to 100 million copies every month, according to historian David Hadju’s “Ten-Cent Plague.” Sales bombed after a public backlash against horror comics led to publishers self-censoring (resulting in a lot of boring stories). Then came television. Publishers dropped like flies.

But after a few years trying to write interesting stories where nothing bad was allowed to happen, creators came up with some ingenious workarounds — namely the rise of superheroes at DC and Marvel. The industry was saved.

For 20 years. In the 1970s, the traditional method of distributing comics was drying up. Comics were stocked in drugstores the same way magazines were: The distributor would show up once a week, put the new periodicals out, and take the unsold ones away — which were sent back to the publisher for a refund.

Comic book sales fell off another cliff. Until a retailer named Phil Seuling came up with the idea of the “direct market.” In this scheme, publishers could sell comics directly to retailers. It meant the end of returns — retailers would agree to keep all the books they ordered, and the publishers would agree to a lower wholesale price. The comic book store was born. Once again, ingenuity came to the rescue.

For another 20 years, that is. What went wrong in the late ’90s was a host of problems that all came to roost at the same time, a perfect storm that drove Marvel into bankruptcy. If you ever wondered why Universal owns distribution rights to the Hulk, and Sony has its clutches on Spider-Man, this is the reason. A drowning Marvel sold off its movie/TV assets to stay afloat. The fire sale kept Marvel afloat for a few years — which turned out to be all it needed. Because all those assets they sold off started to make money. Despite having sold off its crown jewels, Marvel realized it was still sitting on a gold mine. It started its own studio in 2005, and three years later launched a B-list character named “Iron Man” onto the silver screen. The rest everyone knows.

And now both major comics companies are nestled safely in the protective bosom of huge corporations — Marvel at Disney, DC at WarnerMedia — who transform the publishers’ IP into big bucks. The future seemed assured.

Until the pandemic. Once again, the comic industry is in existential crisis. Once again, our heroes face certain doom.

So, you know, business as usual.