U.S. stocks dropped on Thursday, as first quarter gross domestic product came in weaker than expected. The economy expanded by only 0.5 percent during first quarter, missing estimates of 0.7 percent. The reading was less than the previous estimate of 1.4 percent. Plus, weekly jobless claims rose by 9,000 to 257,000 - the four-week average fell slightly to 256,000. Meanwhile, the Bank of Japan left key interest rates unchanged and in negative territory. The central bank shocked markets back in February when it pushed these rates into the red. Economists say it's too early to tell if these measures will lift growth in Japan. 'They want to wait and see what the impact of their actions are,' said Steve Blitz, chief economist at ITG. 'Monetary policy, regardless of the nation, takes anywhere between 12 and 18 months before you really see the impact of it.' Ford (F - Get Report) posted first quarter earnings of $0.69 a share, crushing estimates of $0.45 a share, driven by strength from North America sales. Finally, St. Jude Medical (STJ) is being acquired by Abbott Laboratories (ABT - Get Report) in a deal valued at $25 billion, or about $85 a share, which is a 37 percent premium to St. Jude's closing price on Wednesday. TheStreeet's Scott Gamm reports from Wall Street.