This week, these ten stocks have the worst year-to-date performance. Each of these also rates an “F” (“strong sell”) on Portfolio Grader.

Share prices of RentACenter, Inc. (RCII) are down 22.1% since the first of the year. Rent-A-Center operates in the rent-to-own industry in the United States. As of April 24, 2014, 18.7% of outstanding RentACenter, Inc. shares were held short. For more information, get Portfolio Grader’s complete analysis of RCII stock.

Since January 1, Infinity Pharmaceuticals, Inc. (INFI) has fallen 22.1%. Infinity Pharmaceuticals researches and develops cancer drugs. For more information, get Portfolio Grader’s complete analysis of INFI stock.

Shares of Quality Systems, Inc. (QSII) have dipped 22.3% since the first of the year. Quality Systems develops and markets healthcare information systems. Trade volume is up 199.2% from the previous week. The stock’s trailing PE Ratio is 133.70. For more information, get Portfolio Grader’s complete analysis of QSII stock.

Since January 1, American Eagle Outfitters, Inc. (AEO) has plunged 23.6%. American Eagle Outfitters designs, markets, and sells its own brand of low-price clothing, accessories, and personal care products for young adults. The stock has a trailing PE Ratio of 26.40. For more information, get Portfolio Grader’s complete analysis of AEO stock.

Since the first of the year, the price of Clean Energy Fuels (CLNE) is down 29.2%. Clean Energy Fuels sells natural gas fueling solutions to its customers mainly in the United States and Canada. As of April 24, 2014, 19.9% of outstanding Clean Energy Fuels shares were held short. For more information, get Portfolio Grader’s complete analysis of CLNE stock.

The price of Alpha Natural Resources, Inc. (ANR) is down 31.2% since the first of the year. Alpha Natural Resources produces, processes and sells steam and metallurgical coal. As of April 24, 2014, 22.5% of outstanding Alpha Natural Resources, Inc. shares were held short. For more information, get Portfolio Grader’s complete analysis of ANR stock.

Since the first of the year, Weight Watchers International, Inc. (WTW) has tumbled 35.5%. Weight Watchers is a provider of weight management services, operating globally through a network of company-owned and franchise operations. As of April 24, 2014, 19.1% of outstanding Weight Watchers International, Inc. shares were held short. Shares of the stock are being traded at a very rapid pace, up 120.3% from the week prior. For more information, get Portfolio Grader’s complete analysis of WTW stock.

The price of UTi Worldwide (UTIW) has fallen 39.5% since the first of the year. UTi Worldwide is a supply chain services and solutions company. As of April 24, 2014, 10% of outstanding UTi Worldwide shares were held short. For more information, get Portfolio Grader’s complete analysis of UTIW stock.

Shares of Walter Energy (WLT) have slumped 46.6% since the first of the year. Walter Energy is a producer and exporter of metallurgical coal for the global steel industry. As of April 24, 2014, 13.3% of outstanding Walter Energy shares were held short. For more information, get Portfolio Grader’s complete analysis of WLT stock.

Shares of Aeropostale, Inc. (ARO) have slipped 47.1% since January 1. Aeropostale is a mall-based specialty retailer of casual apparel and accessories. As of April 24, 2014, 28.5% of outstanding Aeropostale, Inc. shares were held short. For more information, get Portfolio Grader’s complete analysis of ARO 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.