Health plan premium increases are again cracking double digits, according to two important gauges of benefit costs.

Sherlock Co., which analyzes managed care companies, says to anticipate an 11.4-percent hike in premium rates next year, with the highest increases in the mountain states.

Actual experience may bear Sherlock's forecast out, if the Federal Employees Health Benefits Program is any indication. Premiums for participating plans will rise an average of 10.5 percent, beginning Jan. 1, 2001. The program covers 9 million federal workers, dependents, and retirees.