This week, these ten stocks have the worst year-to-date performance. Each of these also rates an “F” (“strong sell”) on Portfolio Grader. Since the beginning of the year, the Nasdaq is up 14.9%, the Dow rose 6.9%, and the S&P is up 12.4%.

Shares of Pengrowth Energy (NYSE:PGH) have dipped 53.3% since the first of the year. Pengrowth Energy Trust is an energy investment trust that acquires, owns, and operates interests in oil and natural gas properties in Canada. For more information, get Portfolio Grader’s complete analysis of PGH stock.

Shares of Advanced Micro Devices (NYSE:AMD) have fallen 55.6% since January 1. Advanced Micro Devices is a global semiconductor company that provides processing solutions for the computing and graphics markets and is involved with manufacturing, research and development, and sales. As of Dec. 20, 2012, 20.4% of outstanding Advanced Micro Devices shares were held short. For more information, get Portfolio Grader’s complete analysis of AMD stock.

Shares of Molycorp (NYSE:MCP) have slumped 57.9% since January 1. Molycorp produces rare earth products, including oxides, metals, alloys and magnets for a variety of applications including clean energy technologies, technology, and defense applications. As of Dec. 20, 2012, 24.8% of outstanding Molycorp shares were held short. For more information, get Portfolio Grader’s complete analysis of MCP stock.

The price of Key Energy Services (NYSE:KEG) is down 58.1% since the first of the year. Key Energy Services provides onshore, rig-based well services, including well maintenance, workover, completion and re-completion, and plugging and abandonment. The stock’s trailing PE Ratio is 32.60. For more information, get Portfolio Grader’s complete analysis of KEG stock.

Since January 1, WebMD (NASDAQ:WBMD) has fallen 58.5%. WebMD is a provider of health information services to consumers, physicians and other healthcare professionals, employers and health plans through our public and private online portals and health-focused publications. The stock has a trailing PE Ratio of 270.30. For more information, get Portfolio Grader’s complete analysis of WBMD stock.

Since the first of the year, the price of YPF (NYSE:YPF) is down 59.7%. YPF is an energy company operating a fully integrated oil and gas chain with market positions across the domestic upstream and downstream segments. For more information, get Portfolio Grader’s complete analysis of YPF stock.

Since the first of the year, SUPERVALU Inc. (NYSE:SVU) has dipped 66.7%. SUPERVALU operates as a grocery retailer that also provides supply chain services, mainly wholesale distribution. As of Dec. 20, 2012, 39.4% of outstanding SUPERVALU Inc. shares were held short. For more information, get Portfolio Grader’s complete analysis of SVU stock.

Shares of NII Holdings (NASDAQ:NIHD) have sunk 70.4% since the first of the year. NII Holdings provides mobile communications for business customers in Latin America. As of Dec. 20, 2012, 36.7% of outstanding NII Holdings shares were held short. For more information, get Portfolio Grader’s complete analysis of NIHD stock.

Share prices of Knight Capital Grou (NYSE:KCG) are down 72.9% since the first of the year. Knight Capital Group provides trade execution services across multiple asset classes. For more information, get Portfolio Grader’s complete analysis of KCG stock.

Shares of Education Management Corp. (NASDAQ:EDMC) have slumped 83.6% since the first of the year. Education Management is the provider of post-secondary education in North America that offers academic programs to its students through campus-based and online instruction, or through a combination of both. For more information, get Portfolio Grader’s complete analysis of EDMC stock.

Louis Navellier’s proprietary Portfolio Grader stock ranking system assesses roughly 5,000 companies every week based on a number of fundamental and quantitative measures. Stocks are given a letter grade based on their results — with A being “strong buy,” and F being “strong sell.” Explore the tool here.