Mass discount retailers entered the market since 1960s. A typical example is Wal-Mart. They originally (and most of them still) targeted at lower-income customers and offered broader lines of products than department stores like the Macy's and Sears. In 1960, the combined sales of discounters were $2 billion and that of Wal-Mart alone increased to $218 billion for the fiscal year ended January 31, 2001. While mass discounters continued to prospered, another type of discounters were introduced in the early 1980s - wholesale clubs. Take Costco as an example, the company became the largest wholesale club in the industry with sales of $34 billion in 2001. Although it is smaller than Wal-Mart, Costco adopt a different set of business strategy and delivered its value in a different way.

Compare Wal-Mart vs. Costco Wholesale Corporation and list the business strategies (different from Wal-Mart's) that Costco employs to deliver value to its customers. Note: news articles and company's annual reports could be good source of evidence.