Michael Bloomberg, former New York mayor and president and CEO of Bloomberg LP. (Christophe Petit Tesson/EPA)

Bloomberg, my former employer, is reportedly moving to a paywall. If that turns out to be true, I can’t say I’ll be surprised.

When I announced that I was leaving Bloomberg View for the Post Opinion section in February, many longtime readers gently reproached me for moving my writing behind a subscriber paywall. Some of them were not so gentle. How could I cut myself off from readers like that? Was I really so arrogant as to think they ought to pay for the privilege of reading me?

I couldn’t blame them for being miffed; some of them, after all, had been reading me since I was a young(ish) blogger writing from Ground Zero. The open Internet literally gave me my career, and for years, I’ve repaid that gift by seeking out employers that kept my writing free to readers. I really believed in the motto that “information wants to be free.”

But by the time The Post approached me, I’d already concluded that the battle for the open Internet was lost. Sooner or later, virtually everyone in the industry is going to put his or her content behind a subscription wall. And in general, you should bet on “sooner” rather than “later.” This week, Vanity Fair became just the latest in a long line of publications to say “If you want to read us, you’ll have to subscribe.”

As New York University journalism professor Jay Rosen noted on Twitter, Bloomberg already has “one of the greatest subsidy systems ever invented”: the terminals that it sells to financial companies at a cost of $20,000 per user per year. If they still want a paywall, we should be bearish on the chances that anyone else in the news business will make a go of the “free content” model.

So how did my industry make it work for so long? The answer is that we never did, really, which is why so many newspapers and magazines are struggling to stay afloat, and so many Web publications are burning through piles of investor money as they hunt for a viable business model. The more interesting question is why we couldn’t make it work. And the answer to that lies in the structure of the traditional media business.

Critics of the “mainstream media” (or if you prefer, the “lamestream media”) are fond of saying that we’re going to be put out of business by competition from “new media” upstarts. Indeed, as a young blogger, I might even have made a few such pronouncements. And I and those critics were wrong. Traditional media can survive competition for readers just fine. It’s competition for advertisers that’s killing us.

For more than a century, magazines and newspapers were what’s known as a “two-sided market”: We sold subscriptions to you, our readers, and once you’d subscribed, we sold your eyeballs to our advertisers. That was necessary because, unbeknownst to you, your subscription dollars often didn’t even cover the cost of printing and delivering the physical pieces of paper. They rarely covered much, if any, of the cost of actually reporting and writing the stories printed on those pages. And you’d probably be astonished at how expensive it is to report a single, relatively simple story.

But that was okay, because we controlled a valuable pipeline to reader eyeballs — a pipeline advertisers wanted to fill with information about their products. You guys got your journalism on the cheap, and advertisers got the opportunity to tell you about the fantastic incentive package available to qualified buyers on the brand-new 1985 Chevy Impala.

Then the Internet came along, and suddenly, we didn’t own the only pipeline anymore. Anyone can throw up a Web page. And over the past 20 years, anyone did — far more than could support actual advertiser demand.

The companies that won this rugby scrum weren’t the venerable old names with long experience marrying ads to winsome content. They weren’t even the new media companies with their frantic brigades of young staffers generating hot takes. The companies that are winning — mostly Google and Facebook — get content for free from their users, or other people on the Internet. Including us.

Providing the rope with which someone else will hang you is obviously not a very good business model. And in the words of economist Herb Stein, “If something can’t go on forever, it will stop.” Either we will find someone else to pay for the news and opinion and cartoons you consume, or we will go out of business.

That someone doesn’t have to be the reader. Some journalism can function as a sort of a loss leader for a conference business, or another associated product, like books or package tours. Some opinion writing can be produced by people who use it as a personal loss leader for their brand as a “thought leader” or “public intellectual” — or simply use it as a hobby to blow off steam. Outside of the “loss leader model,” there are a few other options: Some reporting can be financed by donors as a philanthropic project; some consumer product journalism can support itself through affiliate programs that provide rewards for selling merchandise; and some writing can be supported by “native advertising” sprinkled among the journalism so that it’s hard to tell them apart. All of those business models can produce good journalism.

But all of those strategies also have flaws. You need a pretty affluent demographic and a highly prestigious brand for the “loss leader” strategy to work. And while opinion writing is very important (she said, modestly), it’s not the only important work we do; academics and business executives are largely not going to pick up the unglamorous but necessary job of beat reporting. Philanthropic journalism can take up some of that slack, but it will be narrow in another way: Donor-funded journalism tends to largely be ideological, with donors looking for stories that flatter their opinions and produce measurable political “impact” beyond just keeping readers informed. A lot of that journalism is very valuable — but it’s not all that we need. And as for the last two models, I presumably don’t have to explain the dangerous incentives built into them.

But if you don’t like those options, then you, dear reader, are going to have to step up to the plate. Unfortunately, many of you have gotten used to the idea that news ought to be free, and resent being asked to pay for it.

At the moment, in concession to your feelings on the subject, most paywalls are relatively porous. (Yes, we know about the tricks you use to subvert them.) But as more and more publications move behind paywalls, you should probably expect that to change. The less we have to worry about competition from free sites, the more those paywalls will tighten. (To be clear, this reflects my opinion based on analysis of industry-wide economics, not any knowledge of employer business strategy, current or former.)

And that will be a sad thing, because the old open Internet was a marvelous gift to readers, a vast cornucopia of great writing upon which we’ve been gorging for the past two decades. But there’s a limit to how long one can keep handing out gifts without some reciprocity. At the end of the day, however much information wants to be free, writers still want to get paid.