Diamond Comic Distributors' comic market share figures for September show DC closing the gap between it and leader Marvel by about 4% of share when reorders and other shipment impacts are included.  This is a greater shift than the 2% difference last month (see 'Comic Shipment Shares Closer to Preorders in August'), but still less than the 6% shift in July (see 'Diamond Releases Comic Shipment Market Shares').  The shipment numbers are based on actual shipments to stores; prior to July of this year, Diamond has published only market share figures based on initial advance orders. 

We've speculated here in the past that the fact that DC overprints substantially on its most popular titles while Marvel has negligible overprints is one factor that leads to DC gaining share when reorders are included.  One factor that might be leading to smaller differences between initial and final shares, at least with respect to Marvel and DC, is Marvel's changing advance reorder policy.  Since Diamond's initial market share numbers are based on initial advance orders only, orders placed between that cut-off and when print runs are set cause part of the difference between the two market share numbers.  Marvel has recently extended its cutoff for advance reorders to dates closer to shipment.  This may be allowing retailers to get more of what they need on Marvels and be reducing the impact of DC's more liberal reorder and overprint policies.  Regardless, a 4% share swing is still substantial, and points out the importance of overprints and backlist on over-all sales by comic publishers. 

Market shares of three smaller publishers were larger when reorders and backlist were included -- Dark Horse, Viz, and CrossGen.  Dark Horse and Viz have substantial graphic novel backlists in print, and CrossGen has a liberal overprint policy on its new comic issues.

Of course in addition to overprints and backlist, scheduling issues can also have an impact on share differences between initial orders and final shipments -- titles that shift into or out of a reporting period make a difference.