The U.S. Consumer Sentiment Index tumbled in July, falling 9.5 points, according to the University of Michigan. Strange thing is, nobody knows why. According to researchers, the sentiment index doesn’t drop this much unless something really big shocks the economy and the national psyche. The shocking thing about this month’s decline is that nothing really shocking happened between June and July. In fact, in the 32-year history of this survey, it’s fallen by 9.5 points or mor...