Several weeks ago, Merrill Lynch downgraded Wal-Mart ( WMT) to neutral from buy, citing higher energy costs and slower sales trends. The stock dropped 2% on the news to $44.19, and is now trading 13% off its 52-week high of $50.87.Increased interest rates, a potential slowdown in consumer spending, and media reports (and public outrage) over the company's low wages and alleged poor employee benefits also have led to negative sentiment for Wal-Mart. But have the shares of the giant retailer fallen enough that they could be a buy for investors? The short answer is yes. Shares of Wal-Mart, priced below $45, are a sound investment. Wal-Mart's market cap is 4.5 times Target's ( TGT) and 7.4 times that of Costco ( COST), its two closest competitors. Compared with its rivals, Wal-Mart is considered a discount retailer, meaning it caters to consumers with annual average household incomes of less than $30,000. During a general economic slowdown, less-affluent consumers are more likely to tighten their spending habits. With record fuel prices and rising interest rates, the U.S. is expected to see a gradual slowdown in consumer spending. I believe lower-income consumers will be more inclined to shop at Wal-Mart, most notably for groceries. Looking at recent surveys, Wal-Mart's food prices are more than 25% lower than its competitors. Because of an ability to squeeze its suppliers, the company is able to sell items at much lower prices than its competitors. Opponents of Wal-Mart have criticized this tactic. But for an investor, it creates more shareholder value by increasing the amount of foot traffic in stores. Suppliers face the dilemma of either pulling their products out of Wal-Mart stores because of tighter margins or having those products offered to 176 million customers around the world on a weekly basis. Wal-Mart also is changing its demographic reach.