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

The price of Questcor Pharmaceuticals, Inc. (QCOR) has seen a 25.7% boost since the first of the year. Questcor Pharmaceuticals develops and commercializes novel central nervous system-focused therapeutics that address significant unmet medical needs. For more information, get Portfolio Grader’s complete analysis of QCOR stock.

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

Tesla Motors, Inc. (TSLA) has risen 26.7% since the first of the year. Tesla Motors designs, develops, makes and sells fully electric vehicles and components of vehicle powertrains. For more information, get Portfolio Grader’s complete analysis of TSLA stock.

Since January 1, Qihoo 360 Technology Co., Ltd. ADR Class A (QIHU) has jumped 28.5%. 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.

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

Since January 1, Vipshop Holdings Ltd. Sponsored ADR (VIPS) has climbed 29.9%. Vipshop Holdings operates as an online discount retailer for various brands in the People’s Republic of China. For more information, get Portfolio Grader’s complete analysis of VIPS stock.

Shares of Canadian Solar (CSIQ) have risen 32.5% since January 1. Canadian Solar is engaged in the design, development, manufacture, and sale of solar cell and solar module products that convert sunlight into electricity. For more information, get Portfolio Grader’s complete analysis of CSIQ stock.

Since January 1, Illumina, Inc. (ILMN) has shot up 44.9%. 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.

Since the first of the year, the price of Shanda Games Ltd. Sponsored ADR Class A (GAME) has swelled 47.7%. Shanda Games develops, sources, and operates Internet games in China. For more information, get Portfolio Grader’s complete analysis of GAME stock.

Shares of Insys Therapeutics, Inc. (INSY) have leapt 50.4% since January 1. 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.