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 79 points (0.5%) at 15,295 as of Wednesday, May 15, 2013, 12:45 PM ET. The NYSE advances/declines ratio sits at 1,703 issues advancing vs. 1,237 declining with 128 unchanged. The Basic Materials sector currently sits down 0.41 versus the S&P 500, which is up 0.6%. On the negative front, top decliners within the sector include Barrick Gold Corporation ( ABX), down 3.27, Apache Corporation ( APA), down 1.42, Canadian Natural Resources ( CNQ), down 1.39, Schlumberger ( SLB), down 1.17 and Total ( TOT), down 0.87. Top gainers within the sector include YPF Sociedad Anonima ( YPF), up 8.2%, Valero Energy Corporation ( VLO), up 2.9%, Marathon Petroleum ( MPC), up 2.6%, Phillips 66 ( PSX), up 1.9% and Freeport-McMoRan Copper & Gold ( FCX), up 1.6%. TheStreet Ratings group would like to highlight 5 stocks pushing the sector lower today: 5. POSCO ( PKX) is one of the companies pushing the Basic Materials sector lower today. As of noon trading, POSCO is down $0.96 (-1.3%) to $71.87 on light volume Thus far, 76,719 shares of POSCO exchanged hands as compared to its average daily volume of 291,600 shares. The stock has ranged in price between $71.56-$72.36 after having opened the day at $72.01 as compared to the previous trading day's close of $72.83. POSCO engages in the manufacture and sale of steel products in Korea and internationally. POSCO has a market cap of $22.4 billion and is part of the metals & mining industry. The company has a P/E ratio of 5.9, below the S&P 500 P/E ratio of 17.7. Shares are down 11.3% year to date as of the close of trading on Tuesday. TheStreet Ratings rates POSCO as a hold. Among the primary strengths of the company is its attractive valuation levels, considering its current price compared to earnings, book value and other measures. At the same time, however, we also find weaknesses including a generally disappointing performance in the stock itself, disappointing return on equity and feeble growth in the company's earnings per share. Get the full POSCO 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.