* For the third time in two years, Allstate said it will lower auto insurance rates in California by an average of 5.1%. Allstate implemented a 7% auto rate reduction in January 1997 and a 2.7% decrease in July 1996. The company said the latest reduction was due in part to improved claims operations and the enactment of Proposition 213, which prohibits drunk drivers and uninsured motorists from suing for punitive damages. The reduction will take effect Aug. 24 for renewals.
* Santa Barbara-based Tenet Healthcare Corp., the second-largest hospital operator in the U.S., said it plans to buy a majority stake in a Boston-area medical system from Columbia/HCA Healthcare Corp. to increase its share of the Massachusetts health-care market. Tenet signed a letter of intent to buy Columbia's 80% interest in MetroWest Medical Center, which primarily operates two hospitals in Framingham and Natick. Terms weren't disclosed.