Tesla Motors Inc (TSLA): Why Wall Street Questions Monthly Model S Sales Estimates

Tesla Motors Inc. sold 1,652 Model S luxury electric cars in the U.S. last month, 50 percent more than in May 2014, according to an estimate from WardsAuto. But analysts point out that the numbers are ballpark figures based on state vehicle registrations and shouldn't be used to measure how well the company is achieving its goal of selling 55,000 cars worldwide this year.