There’s an interesting analysis by Todd Allen here that looks at some recent numbers to analyse the trends: http://www.comicsbeat.com/whats-a-hit-comic-sell-these-days-over-40k-for-marvel-over-30k-for-dc/
I won’t copy and paste the full article, but it’s worth clicking through to look at the charts and see how this conclusion is reached:
[quote]On the whole, the stories you read about how great the comics sales are boil down to more issues of lower selling titles. The big hits aren’t as common and when the BIG hits drop, they tend to be Events and aided by variant covers. The ongoing series — the normal issues, if you will — keep drifting down. Even the current Big Three titles of Star Wars, Batman and Darth Vader have been drifting down a bit in recent months. Scott Snyder and Greg Capullo aren’t going to be making Batman comics forever and DC is going to have BIG shoes to fill when those two say their final farewells to the franchise. The “normal,” ongoing title have softer sales for the most part.
It’s the mid-list and below that’s driving the market, except it isn’t the really what we would have called the mid-list 5 years ago.
Take a good hard look at all those titles clustered between 20K-39K. If you hear creators lamenting a decline in royalties, they likely aren’t exaggerating. Diamond will be just fine with more small titles. The publishers will be OK if they can pump out enough of them, although the standard attrition will start making that a bit more extreme if it keeps up. Of course, the more titles you publish, the more sales get split between titles. It’s a lot like cable sapping the broadcast network ratings.
Retailers could use a few more hits. Low copy per issue sales makes it harder for them to order copies for the shelf (hence the constant creator requests for readers to pre-order). Having a few titles that sell 100 copies each makes it a lot easier on the ledger to have a shelf copy of one of those lower selling titles sitting on the shelf. Without the big hits, there’s more incentive to take it easy on the shelf copies and err on the side of caution.
It’s a strange time as we wait for Rebirth and Civil War II and the Big Two’s attempt to get some higher per issue sales in the mix.[/quote]