As Bleeding Cool pointed out over the weekend, the Diamond sales charts for April might be a little bit misleading. Though Secret Empire #0 topped the chart according to Diamond's listing and writer Nick Spencer's twitter, it was not actually been the top selling comic. According to the recently released Top 100 index from Diamond, both Batman #21 by Tom King and Jason Fabok and The Flash #21 by Joshua Williamson and Howard Porter, part of DC's The Button crossover, were higher sellers than Secret Empire #0.
To figure this out, we need to look at the Diamond Sales Index number for each title:
The index column is described by Diamond thusly:
The Sales Index of selected monthly Best Seller Charts is presented as a comparative tool for retailers and publishers. It presents Diamond's monthly sales for individual titles in relation to Diamond's total sales for the issue of DC Comics' monthly Batman comic book. (Batman is used as the control title – with a value of 100 – because sales of Batman usually remain relatively stable.
So these are not numbers, but a proportional representation of how comics performed against each other, with Batman always set at 100. What this means is that, if Batman #21, with index of 100, sold 100,000 copies, then Secret Empire #0, with an index of 124.96, sold 124,960 copies. Those may not be the exact numbers, but they will be proportional no matter what. For instance, if Batman #21 sold 500,000 copies, than that would mean that Secret Empire #0 sold 624,580 copies. Got it?
Okay, well, here's were things get interesting. Both Batman #21 and The Flash #21 were split into two groups, one with lenticular covers, and one without. Though variant covers are normally grouped together, the reason here appears to be the price difference, with the lenticular editions costing a full dollar more than the non-lenticular versions (though we're reaching out to Diamond for clarification). But when looking at which comics sold more copies, it makes sense to combine the numbers, and if we do that, Batman #21 actually has an index of 168.54, a full forty points higher than Secret Empire #0. If Batman #21 Lenticular Edition sold 100,000 copies, that means Batman #21 non-lenticular sold 68,540. Again, these are not the actual units sold, but the proportional relationship remains the same no matter what the actual numbers are. What it means is that Batman #21 was the top selling comic in April, according to Diamond's statistics.
But that's not all! The Flash #21, Lenticular Edition, was ranked at #5 with an index of 82.2, while The Flash #21 non-lenticular edition was ranked at #11 with an index of 52.04. When we combine these, we get an index of 134.24, which means The Flash #21 also outsold Secret Empire #0 in April as the number two best-selling comic of the month.
Without knowing the actual unit sales, it may impossible to get a truly accurate picture of exactly how many comics each book sold, though some sites do their best to come up with estimates. But the index does provide, as Diamond calls it, a "comparative tool" to figure out how these comics sold in relation to each other. And according to that comparison, when removing the artificial division between two different versions of Batman #21 and The Flash #21, Secret Empire #0 was the third best selling comic of April, and DC's The Button crossover is thus far the more successful of the two events. That's not to say it did bad — third place is still worth a bronze medal in the Olympics.
It's just that this…
…is not technically true. It was a best-selling comic, but not the best-selling. And accuracy is important.
Another factor important to remember is that Diamond's sales charts represent comics sold to retailers, not comics sold by retailers to readers. Though, on Bleeding Cool's April 23 bestseller list that looks at a sample of that from participating retailers, Batman #21 topped the charts as well, with Secret Empire #0 coming in at #4. Of course, Secret Empire #1 could perform far better than Secret Empire #0, as readers might view zero issues as less vital to the series, so we'll be keeping an eye out for May's numbers to see how things are looking then.