New figures show the once-soaring housing market in California continuing an earthbound descent. According to an index that tracks home sales in major metropolitan areas, the price of a single-family home in June fell an average of 15.9% from last year. But the same index, the Standard & Poor’s Case-Shiller Composite-20, released Tuesday, also reported a 25.3% price drop in Los Angeles, a 24.2% decline in San Diego and a 23.7% drop in the San Francisco Bay Area. Only Las Vegas, Miami and Phoenix fared worse, with home prices falling 28.6%, 28.3% and 27.9%, respectively.