Bucking a national trend, manufacturing in Orange County stalled in the second quarter, but should improve in the second half of the year, according to a Chapman University report. The university's Orange County manufacturing index, which tracks industry's expansion and shrinkage, fell to 50.7 in the three months ended June 30, from 58.6 in the first quarter. An index reading in excess of 50 indicates the manufacturing segment is growing, while a reading lower than 50 reflects a contraction. Nationally, the manufacturing index jumped to 55 from 52.1. Orange County's high-tech sector, an engine in recent years for the county's booming economy, showed no growth in the second quarter. Chapman economists recently predicted that high-tech employment would grow this year by only 1.2%, compared with a blistering 7.8% last year. Manufacturing accounts for about 18% of the county's total employment.