The first half of 2017 was a fantastic period for U.S. stocks, which are key to growth of capital in broadly diversified portfolios invested for the long run. Stocks posted a 2.9% gain in the second quarter of 2017 following a 6.1% gain in the first quarter. This followed a return of 3.8% in the fourth quarter of 2016, 3.9% in the third quarter of 2016, and 2.5% in the quarter before that.