I'm not sure that judging a retail sales strategy by change in sales between January and April of 2009 -- exactly the period when consumer confidence plummeted to match the tanking Dow -- is a great idea.

For comparison, line up this chart

http://finance.yahoo.com/echarts?s=^DJI+Interactive#chart1:s...

with the one in the article...

I guess the test will be whether sales will shoot up when they reverse this policy.

(The article also doesn't say anything about whether they tested this approach in some stores before converting all stores; Walmart has a long history of mining their sales data to try to pick out patterns in store performance, so if this was done as abruptly as the article says, I'm surprised.)