Using Langeveld’s rules, New York Times would keep $15 million in ad revenue, lose $135 million in ad revenue and gain $240 million a year in subscription revenue. That’s a $105 million a year gain for the Times, or a 70 percent increase over ad-only revenue.

Now, these remaining customers, who will spend much more time on the site and would be a more desirable (richer) demographic are worth much more than the nonpaying reader who pops in for twenty seconds from a link emailed from her brother. So the retained ad revenue would be higher, making this an even better proposition.

Now, I don’t believe the Times could get two million subscribers to pay $120 a year—at least not right away. I’m just using Langeveld’s own rules for his experiment to illustrate how it would work.

But the bigger problem with Langeveld’s analysis is it posits an all-or-nothing content wall. Nobody’s proposing that. Even The Wall Street Journal, the most successful (and one of the only) newspaper to charge, gives most of its content away for free. And he makes a mistake here:

Or consider that the Wall Street Journal has about a million paying subscribers at $8.66 a month, versus 14 million monthly UVs at the free New York Times site. Print circulation for the two are roughly equivalent, but the Journal’s fee cuts its online audience to just 7 percent of the Times’s.

The Journal’s fee does not cut its traffic to seven percent of the NYT’s. The Journal Online gets about 7 million unique users a month, compared to the Times’s 20 million, according to Nielsen Online. (The Journal itself maintains that Nielsen grossly underestimates its traffic, which it says brings in 23 million unique visitors a month.) That’s 35 percent of the Times’s traffic, not 7 percent.

The Journal has done that by a pretty clever system that lets nonsubscribers read stories that are linked to by others like Google News and Digg, while making it difficult to be a heavy reader without subscribing.

In that way, it has kept its 1.1 million online subscribers (which I’ve estimated pay $50 million or $60 million a year), while benefiting from the spike in traffic from nonsubscribers than can come to a popular story.

Also important: It seems to me that charging online would help newspapers slow their print circulation declines, and perhaps even give them a bit of pricing power on rates. Remember a print reader is still worth about nine times the revenue a (non-paying) online one is. I’ve said this till I’m blue in the face, but I‘ll repeat it:

Newspapers make fools of all their paying subscribers by giving their product away free on the Web. Why pay $400 a year for The New York Times when the same thing is free online? I sure could use that extra $35 a month, and it’s mighty tempting to kill my subscription—I don’t like the actual print product that much. If that happens, the NYT loses 90 percent of my value to it in the form of lost revenue.

At the very least, this might give papers some breathing room to survive this economic crash.

Readers need to know that it takes a lot of money and effort to produce good reporting (not to mention to have that reporting well-written and edited). The free model just won’t support the level of professional reporting we have even now, after all the industry’s layoffs.

But most critically, Langeveld, who says in his headline “Sorry, but the math just doesn’t work” for charging online doesn’t acknowledge the more-obvious point: neither does not charging.

What do papers have to lose?

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Ryan Chittum is a former Wall Street Journal reporter, and deputy editor of The Audit, CJR's business section. If you see notable business journalism, give him a heads-up at rc2538@columbia.edu. Follow him on Twitter at @ryanchittum.