Every month, Bleeding Cool takes a look at the marketshare numbers reported by Diamond Comic Distributors. We do our little sums, we work out which company is swinging which way and why, and occasionally draw some spurious conclusions.

But we also try to point out some of the limitations of the data.

It only records comic books sold through the direct market by one distribution, Diamond. And only in North America, any other sales, including a significant 5-15% sold to the UK, is dismissed.

Diamond defines what counts as a comic or a graphic novel towards marketshare. Dark Horse's Zelda book has never counted, despite containing a number of comics within.

It does include orders by Loot Crate and Nerd Block, if carried out through Diamond, like Orphan Black and Bravest Warriors, taking them to the top of the chart – but not if it was Doctor Who The Eleventh and Twelfth Doctors #1 as that occurred outside of Diamond. None of those sales occurred in comic book stores but such as the power of Loot Crate that it can shift the marketshare of a smaller publisher considerably and send almost any comic to the top of the charts.

It doesn't include, say, the considerable amount of sales made by publishers such as Zenescope, Avatar and Boom at comic book conventions, or sold to book stores (even by Diamond), or sold digitally or sold by subscription. All those foil packed comics that IDW sell into Toys R Us and Target? They might as well not exist when it comes to that figure.

There has also been a history of gaming Diamond and getting the best sales statistics. Sometimes Diamond tackles them, such as Platinum's attempt to make Cowboys And Aliens the best-selling graphic novel of the month, sometimes it doesn't. Overshipping a comic, where a publisher sends two copies for every one ordered, gets recorded on the unit chart (if not on the revenue chart). If there is significant difference between the two positions for a comic, after accounting for different prices of comics. then some of the dark arts has been going on. Making a comic returnable sees Diamond take an arbitrary ten percent off their sales, whether a comic was returned or not. Or if half of them were returned.

Also, the chart only records what was ordered not what was sold. Many comics are ordered in sufficient numbers to meet a target for a promotion – but sit unsold on shelves, eventually liquidated or pulped. Yet every one is recorded on the chart.

But there's nothing wrong with the Diamond chart – as long as you accept it for what it is. Any attempt to draw wider conclusions can only be met with disappointment. And for those who rail against the limitations of that chart – unless companies are going to be willing to volunteer their entire commercially sensitive information, we are never going to see it

Bleeding Cool tries to run a weekly sales chart, but that's restricted to a top ten and only has a handful of regular participating stores (get in touch if you'd like to join them).

We really need better statistics… or corporate espionage.