Editor's Note: TheStreet ratings do not represent the views of TheStreet's staff or its contributors. Ratings are established by computer based on metrics for performance (which includes growth, stock performance, efficiency and valuation) and risk (volatility and solvency). Companies with poor cash flow or high debt levels tend to earn lower ratings in our model All three major indices are trading up today with the Dow Jones Industrial Average ( ^DJI) trading up 153 points (1.0%) at 15,456 as of Tuesday, May 28, 2013, 12:50 PM ET. The NYSE advances/declines ratio sits at 2,106 issues advancing vs. 846 declining with 109 unchanged. The Services sector currently sits up 1.3% versus the S&P 500, which is up 0.9%. On the negative front, top decliners within the sector include Delta Air Lines ( DAL), down 1.23, and FedEx Corporation ( FDX), down 0.85. Top gainers within the sector include Liberty Media Corporation ( LMCA), up 14.0%, Tiffany ( TIF), up 3.5%, Hertz Global Holdings ( HTZ), up 3.4%, MGM Resorts International ( MGM), up 3.4% and Las Vegas Sands ( LVS), up 3.0%. TheStreet Ratings group would like to highlight 3 stocks pushing the sector lower today: 3. McKesson ( MCK) is one of the companies pushing the Services sector lower today. As of noon trading, McKesson is down $1.49 (-1.3%) to $115.82 on average volume Thus far, 789,943 shares of McKesson exchanged hands as compared to its average daily volume of 1.3 million shares. The stock has ranged in price between $115.22-$118.30 after having opened the day at $117.80 as compared to the previous trading day's close of $117.31. McKesson Corporation, together with its subsidiaries, delivers pharmaceuticals, medical supplies, and health care information technologies to the healthcare industry primarily in the United States. It operates in two segments, McKesson Distribution Solutions and McKesson Technology Solutions. McKesson has a market cap of $26.6 billion and is part of the wholesale industry. The company has a P/E ratio of 21.0, above the S&P 500 P/E ratio of 17.7. Shares are up 21.0% year to date as of the close of trading on Friday. TheStreet Ratings rates McKesson as a buy. The company's strengths can be seen in multiple areas, such as its solid stock price performance, good cash flow from operations, largely solid financial position with reasonable debt levels by most measures and notable return on equity. We feel these strengths outweigh the fact that the company has had sub par growth in net income. Get the full McKesson Ratings Report now. Exclusive Offer: Jim Cramer's 'go-to' small/mid-cap guru Bryan Ashenberg only buys stocks he thinks could return 50-100%. See his top picks for 14-days FREE.