Yahoo Finance analysis indicates that Costco Wholesale (Nasdaq: COST) stock has risen only 6% year-to-date, significantly underperforming the S&P 500's approximately 12% gain. Analysts believe that given Costco's current high price-to-earnings ratio of nearly 50x, coupled with concerns about the economic outlook and potential interest rate hikes, the likelihood of its stock price falling after its fourth-quarter earnings report on September 24 is greater than it rising. The Motley Fool Stock Advisor analyst team also did not include Costco in its list of 10 best stocks to buy.