January is usually a fairly slow month for comics and 2009 was no exception. With unit sales down by around a million units from the average sales during the final order era (which start in February 2003 when Diamond switched from released data about pre-orders to released data based on what actually shipped to retailers), January 2009 has the lowest total units for the top 300 since January 2006.
Of course, the 49 items from the December 2008 data which hit stores on January 2nd, 2009 totaled up to around 1,609,540 units in combined sales. Add that to the 5,615,697 units reported on the January list and the total goes up to 7,225,237 units. The obvious problem is this is an apples-to-oranges comparison since more than 300 items are in the revised total for January 2009. Subtracting out the total sales of the bottom 48 items from the January list of 108,822 units results in a total of 7,116,415 units for January 2009. That revised total would be the best January during the final order era.
The reason for adding in the sales of 49 items and only subtracting out 48 items is the top 300 comics list for January 2009 only had 299 unique items on it. In the raw data released by Diamond, "Final Crisis" #6 was mistakenly included a second time on the list at rank 130. I was able to confirm with Diamond that those sales were also included in the entry for "Final Crisis" #6 in rank 3. As such, I removed the duplicate data from the list and moved everything up by one rank. A similar mistake was made on the trades list with the "Walking Dead" vol. 3 trade paperback listed in rank 95 with an estimated 1,040 units at $12.99 and also in rank 160 with an estimated 625 units at $14.99. Since these items are at different prices, it is reasonable to believe that the sales from rank 160 are not included in the sales at rank 95.