An index of San Diego’s economic health rose again in May, marking 12 straight months of positive outlooks, the University of San Diego said Tuesday.

The index, compiled by associate professor Alan Gin, rose 0.5 percent. It was the lowest gain since October.

The gains were driven by significant increases in building permits and the national economic outlook, overcoming a large decline in local stock prices and a modest dip in consumer confidence. The index measured modest gains in initial unemployment insurance claims and help wanted advertising. It was the first time the index featured two negative components since August 2014.

Gin said it was unclear why local stocks dropped 1.2 percent in May as all major market averages increased that month. The drop in consumer confidence was relatively small, at 0.09 percent, but broke a string of 15 months of consecutive increases. Residential units authorized by building permits were up 2 percent, surpassing 1,000 units for the first time since last March.

The USD Burnham-Moores Center for Real Estate’s Index of Leading Economic Indicators for San Diego County stood at 139.7 in May, compared to 138.9 in April.