A closely watched index of future U.S. economic activity rose in July by the most in three months, indicating improving growth in the second half of the year, a private-sector research organization reported Thursday. The Conference Board said its leading economic index—designed to forecast economic activity in the coming three to six months—rose 0.6 percent to 96.0 last month after being flat in June. The July gain was slightly stronger than economists had expected. The improvement suggests "better economic and job growth in the second half of 2013," said Conference Board economist Ken Goldstein. "However, the biggest uncertainties remain the pace of business spending and the impact of slower global growth on U.S. exports." Eight of the 10 indicators in the leading index strengthened in July, led by cheaper borrowing costs, higher stock prices, and more building permits. Gains in factory orders and fewer jobless claims also helped the index last month. The Conference Board's index of coincident indicators, which measure current economic activity, increased 0.2 percent in July, the sixth consecutive monthly gain. The index of lagging indicators, which measures past activity, decreased 0.2 percent last month. The report was in line with other recent economic data. Higher property values tied to the housing-market recovery, along with steady job gains, is keeping consumer spending elevated and has reduced the effects of higher pension taxes.