Favoring stocks in some U.S. industries and avoiding others mattered less in the third quarter than it has in decades. A comparison of the S&P 500 Index’s 11 main industry groups, or sectors, shows as much. The biggest gain was 2.3%, posted by financial stocks, and the largest drop was 4.6% for industrial shares. The gap of 6.9 percentage points between first and last place was the smallest in any quarter since the sector indexes were first calculated in 1989, according to data compiled by Bloomberg. The prior record was 8.1 points, set in 1989’s third quarter.