Auto dealers are hurting all over the United States, but they’re having more trouble in Greater Sacramento. In fact, the region’s new-car franchises have disappeared at a rate two-and-a-half times greater than the national average. According to retail consulting firm Urban Science Applications, the number of new-car franchises operating here shrunk by 13.3 percent in four years. That compares to 5 percent nationwide. Since March, the four-county region lost a least a half-dozen dealerships. Industry sources say nationwide factors -- hard to find credit, high gas prices and decline home values -- hit Sacramento harder.