Summary of this in bullet points

Wal-Mart, BJ Wholesale, and Sam's Club are Costco's top competitors. Headquartered in Bentonville, Arkansas, Sam's Club operates in the retail distributors industry and generates $90billion less earnings compared to Costco. Wal-Mart is the world's biggest retailing chain and similar to Costco, it operates in the retail distributors industry. Wal-Mart records annual revenues300 times that of Costco. BJ Wholesale also competes in the retail distributors industry and has a similar geographical reach as Costco. Other competitors include Amazon, which operates an e-commerce business and has 504,000 more workers than Costco

			Costco	Wal-Mart	BJ Wholesale
Critical success factors		Weight	Rating	Weighted Score	Rating	Weighted Score	Rating	Weighted Score
1	Market share	0.10	2	0.20	2	0.20	1	1.10
2	Product quality	0.40	3	1.20	4	1.60	3	1.20
3	Costumer loyalty	0.30	4	1.20	3	0.90	3	0.90
4	Costumer service	0.10	1	0.10	2	0.20	2	0.20
5	Price Competitive	0.10	2	0.20	1	0.10	2	0.20
Total		1.00		2.90		3.00		2.60

The matrix outlines that Wal-Mart is the strongest market rival that Costco faces. However, these figures only outline the relative strengths among the firms, they aim at evaluating and assimilating information in a meaningful way for a firm, to aid in their decision making.