Stock prices of the Valley 50 moved lower along with the broader market for the two-week period ended Oct. 9. Investor concern about the federal government shutdown pushed down the markets. In the Valley, biotechnology stocks showed the most volatility with bioenergy crop company Ceres Inc. gaining 47 percent as analysts’ consensus estimate was more than triple its trading price. On the other side of the spectrum, insulin research firm MannKind Corp. dropped 20 percent. In terms of volume, MannKind placed second with an average of more than 5.7 million shares traded daily, beating the much larger biotech firm Amgen Inc. with 3.3 million shares.