What do investors do when the Fed says the economy is not as strong as thought, when housing numbers fade out, when China shows weak numbers, when Alcoa signals a tough time for metals, when Wal-Mart sees weakness ahead and cuts its growth forecast? In that case, you get a Thursday where investors flee into growth sectors and stocks for returns. Investors rotated money back into biotech, Gilead , Celgene and BioMarin .