Marc-Oliver Frisch writes at The Beat:
Average DC Comics periodical sales in the direct market dropped to their lowest point yet in March 2009, in the context of the six years worth of available data. One reason for that was that the Vertigo and WildStorm imprints remained at very low averages for their periodical lines.
Mainly, though, the decrease is down to the fact that the publisher’s DC Universe department, which traditionally has the highest periodical sales among the three imprints, only released 36 new periodicals in March, as opposed to 45 in February, 51 in January and between 48 and 63 per month in 2008. Taken on their own terms, average DC Universe periodical sales were actually slightly up against February.
While a few DC Universe series did miss their March 2009 shipping dates, however, the draught is mostly down to the simple fact that the line just didn’t publish a lot of comics in March.