WASHINGTON — A gauge designed to predict the economy’s future health posted the sharpest advance in four months in July, indicating the economy is gaining traction headed into the last half of the year.

The Conference Board says its index of leading indicators rose 0.9 percent last month, the sixth straight increase and the best showing since a 1 percent rise in March. The index, composed of 10 forward-pointing indicators, had risen 0.6 percent in June.

A big rise in applications for building permits was a key source of strength in July.

Conference Board economist Ken Goldstein says while retail sales were a bit disappointing last month, the economy was helped by strong hiring gains and increased factory production.