I caught this article about North Jersey comic book stores, and it had a couple of interesting figures I'd never seen put together in quite this way before. First, "North American comic book sales reached almost $518 million in 2013" -- nothing particularly noteworthy or new there. They even cite Comichron.com as the source.
But the other significant number they throw out is that "People who buy comics tend to have a $40 weekly budget." Now, I'm sure this is not an exact number and it's more anecdotal than not. But it is coming directly from a comics retailer, so I'm sure it's more accurate than any survey someone like myself might conduct.
Now, before I start doing anything clever, one of the questions the comic industry has wrestled with is how many comics fans are actually out there buying stuff. The closest we have are the monthly sales numbers, but there's no way to tell from those how much overlap is between titles. How many of the people who bought Uncanny X-Men also bought Action Comics? And how many of them also bought Amazing Spider-Man? We have no way of knowing, so we can't say if the number of fans is simply the cumulative number of all of those sales or (more likely) some percentage less than that.
But if we have an overall sales number and a corresponding sales average, we can apply a little back-of-the-envelope math to get close to the number of people regularly buying comics in North America. So...
$518 million divided by 52 weeks in a year = $9,961,538.46 spent at comic shops every week.
$9,961,538.46 divided by $40 average weekly spend per customer = 249,038.462 customers.
That's a difference of about 18,000. Which suggests that there's not a whole lot of overlap between publishers' readers; if you read DC, you probably don't read much Marvel or Image.
There are of course some caveats here. First, this is only the direct market we're looking at. This doesn't include bookstore sales, digital sales, etc. This is basically only people who walked into a comic specialty shop to buy stuff. Second, that $518 million is comic book sales, but the $40 number also includes action figures, t-shirts, bags & boards, etc.
But, that said, I think this is pretty close to what people are talking about when they're talking about "comic book fans." That's a small enough number -- especially split among multiple publishers -- that I should think that any opportunity to expand on that would have publishers salivating at the opportunity to get more people interested in comics. I see very little of that, though. The latest Ms. Marvel is probably the biggest/best attempt in recent memory, but even that remains restricted by the distribution channels and still seems a little more like shuffling the deck than dealing in new players.
250,000 is the roughly the population of Fort Wayne, IN. Compared to, say, the first Hunger Games book which sold 800,000 copies. Before it was even released in paperback. That's closer to the population of San Francisco.
I don't know that I have a real conclusion here, other than "250,000. Huh. That's a really small number." But it does make me wonder why publishers aren't scrambling to be more aggressive in expanding their reach.