U.S. workers compensation insurers, a group led by Travelers Cos. and Hartford Financial Services Group Inc., posted their first underwriting profit since 2006, helping the industry counter lower yields on bond portfolios.

Insurers had an underwriting profit of 2 cents per every premium dollar, after claims costs and expenses, for a combined ratio of 98 last year, according to preliminary data from the National Council on Compensation Insurance. That compares with a combined ratio of 102 a year earlier and 109 in 2012.

Job-related injuries can emerge long after a policy is sold, meaning that insurers can invest premium dollars for years before paying claims. The companies have found it harder to count on investment income lately, leading them to be more selective about the insurance risks they accept and to raise prices for some types of coverage.

“The reality is, in today’s interest-rate environment, we need to be driving combined ratios under 100,” Steve Klingel, chief executive officer of the group, said in a presentation.

Travelers, Hartford and American International Group Inc. are among companies that have increasingly focused on technology to assess the risks of claims. New York-based AIG has been using data to isolate and contain expenses, such as those tied to excessive use of opiates to treat injuries.

The industry has also benefited from a rebound in U.S. employment. Policy sales for private carriers climbed more than 4 percent last year to $38.5 billion, according to the NCCI.

“Our industry runs in cycles,” Klingel said. “I feel pretty safe in saying that at some point in the future, numbers will deteriorate once again.”