The Chicago Fed's national activity index, which is designed to gauge overall US economic activity, rose to 0.83% in October from a revised 0.32 in the prior mark. That's the first gain in four months.  The CFNAI is a weighted average of 85 existing monthly indicators of national economic activity. It is constructed to have an average value of zero and a standard deviation of one. Since economic activity tends toward trend growth rate over time, a positive index reading corresponds ...