Aetna Inc. is boosting the pay of its lowest-earning employees, joining companies like Starbucks Corp. and Gap Inc. in raising wages as the growing U.S. economy leads to a tighter job market.

About 5,700 employees in areas such as customer service and billing will get a minimum of $16 an hour starting in April, Cynthia Michener, a spokeswoman, said in an e-mail. The company also plans to cover more health-care costs for 7,000 workers beginning next year, she said.

The move is a sign that pressure is growing on employers to increase wages as the labor market gets more active. The U.S. jobless rate fell to 5.6 percent in December, the lowest level since June 2008, though wages dropped 0.2 percent from the previous month. Earnings increased 1.7 percent from a year earlier.