Wal-Mart Stores Inc (WMT.N) is again lifting the lid on its precious data, giving NPD Group access to certain U.S. sales information as the world's largest retailer continues to work on better understanding what its shoppers want.

In the deal announced on Friday, NPD will receive and analyze sales data from Walmart U.S. stores and its website, www.walmart.com, covering merchandise in the entertainment, apparel, home, hardlines, and toy categories.

The agreement with NPD will give Walmart information on what shoppers are buying and what they are looking to buy, Cindy Davis, executive vice president of Walmart global customer insights, said in a statement. Sharing Walmart's point-of-sale information will help it identify opportunities sooner and work with vendors to develop better programs, she added.

Davis was given the task in February 2011 of leading a team to study customer trends. Walmart has felt pressure as consumers, especially those on limited budgets, cut back on purchases and choose to shop more often at dollar stores such as Dollar General Corp (DG.N) and Family Dollar Stores Inc (FDO.N).

Sharing its data and getting analysis from outside companies may help the retail giant better understand what its shoppers are looking for.

The latest pact comes after Wal-Mart said in July 2011 that it would provide sales data from Walmart U.S. to Nielsen Holdings NV (NLSN.N). It also reached a deal that month with another firm, SymphonyIRI, for sharing shopper insights.

NPD said on Friday that it also recently signed an agreement to receive sales information from Wal-Mart's Sam's Club warehouse unit.

(Reporting by Jessica Wohl in Chicago; Editing by Phil Berlowitz)