This week, these ten stocks, all currently earning A’s (“strong buy”) on Portfolio Grader, have the best year-to-date performance.

Since the first of the year, shares of Under Armour, Inc. Class A (UA) have soared 36.5%. Under Armour manufactures performance apparel, footwear, and accessories for men, women and children. Trade volume rose notably over the past week, up 111.5%. For more information, get Portfolio Grader’s complete analysis of UA stock.

Since January 1, the price of PowerSecure International, Inc. (POWR) has grown 39.8%. PowerSecure International provides energy management and conservation solutions to utilities and their commercial, institutional, and industrial customers. For more information, get Portfolio Grader’s complete analysis of POWR stock.

The price of Qihoo 360 Technology Co., Ltd. ADR Class A (QIHU) is up 44.3% since the first of the year. Qihoo 360 Technology provides Internet and mobile security products in the People’s Republic of China. For more information, get Portfolio Grader’s complete analysis of QIHU stock.

Green Plains Renewable Energy, Inc. (GPRE) has risen 47.9% since the first of the year. Green Plains Renewable Energy constructs and operates dry mill, fuel-grade ethanol production facilities. For more information, get Portfolio Grader’s complete analysis of GPRE stock.

Since January 1, Shanda Games Ltd. Sponsored ADR Class A (GAME) has climbed 50%. Shanda Games develops, sources, and operates Internet games in China. For more information, get Portfolio Grader’s complete analysis of GAME stock.

Shares of Illumina, Inc. (ILMN) have risen 57% since January 1. Illumina develops, manufactures and markets integrated systems for the large scale analysis of genetic variation and biological function. For more information, get Portfolio Grader’s complete analysis of ILMN stock.

For more information, get Portfolio Grader’s complete analysis of YY stock.

Since the first of the year, the price of Forest Laboratories, Inc. (FRX) has swelled 66.7%. Forest Laboratories develops, manufactures, and sells both branded and generic forms of ethical products which require a physician’s prescription. For more information, get Portfolio Grader’s complete analysis of FRX stock.

Shares of Rentrak Corporation (RENT) have leapt 68.5% since January 1. Rentrak is an information management company serving the media, entertainment, retail, advertising and manufacturing industries. For more information, get Portfolio Grader’s complete analysis of RENT stock.

Since January 1, Insys Therapeutics, Inc. (INSY) has jumped 81.6%. INSYS Therapeutics develops pharmaceutical products that target the unmet needs of cancer patients, with a focus on cancer-supportive care. For more information, get Portfolio Grader’s complete analysis of INSY 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.