May is the first month for retailers reporting same-store sales since Wal-Mart opted to stop reporting the figure. Wal-Mart in recent years has often outperformed the competition and its weight in the index is such that a good or bad month by Wal-Mart could sway the overall retail figure much higher or lower than it would have been otherwise. As such, it shouldn't be a big surprise that without Wal-Mart's strong sales in the current climate, the May figures look pretty bad.
ICSC's index shows a 4.6 percent decline compared with the same period last year. (The report can be viewed here, membership required.) In contrast, in April retailers posted a same-stores sales gain of 0.7 percent over April 2008. Retail Forward's figure, meanwhile, (computed off 32 retailers) shows a 4.2 percent decline. Retail Forward's April results showed a 0.9 percent increase.
To account for Wal-Mart's exclusion, ICSC has furnished a table detailing the industry's results sans Wal-Mart. I've turned that into a line chart that you can see below. (Click on the thumbnail to see larger version).
CNBC explores similar ground with this story, looking at how the statistics may now be skewed. With numbers like this, it might just be a matter of time before more retailers opt to stop reporting monthly results. You can also see CNBC's rundown of the sales results here. Reuters' summary of the results is here.