Wal-Mart announced that comparable store sales in the U.S. declined (again) in the second quarter of 2011, and overall U.S. sales were flat. However, comps for Walmart Market stores increased 3% from the previous quarter, prompting the mega-retailer to speed up the supermarket’s rollout. So far, the company has announced that about 180 Walmart Market stores are in development.

Wal-Mart also announced that quarterly worldwide sales figures were up 5.5%, and net earnings improved 5.7%.