The biggest health insurer launches second-quarter earnings season for the sector on Thursday when UnitedHealth Group Inc. reports results.

WHAT TO WATCH FOR: Analysts have been watching for any signs that growth in health care use has started speeding up, a trend that could pinch health insurer earnings.

UnitedHealth and other insurers have been helped in recent quarters partially because health care use has grown at a slower pace than they expected when they set premiums. Analysts and other experts say people tend to put off some health care like elective procedures during a slow economy or in the years that follow a recession.

UnitedHealth said in the spring that it saw only a "modest" increase in use in the first quarter. Its biggest expense, medical costs, jumped 6 percent to nearly $20 billion due mostly to increases in the prices charged for care.

The insurer usually trumps analyst expectations for the quarter. Investors like UnitedHealth's business diversity, which helps it handle changes in enrollment or other insurer pressures on profitability. They will be paying attention to the performance of its Optum businesses, which provide services like technology outsourcing and pharmacy benefits management.

The insurer also is the largest provider of Medicare Advantage plans, so investors will be looking for any changes from that segment. Medicare Advantage plans are privately run versions of the government's Medicare program for the elderly and disabled people.

Investors also like UnitedHealth for its dividend. The insurer said last month it would raise its dividend more than 30 percent due in part to strong growth across its businesses. The company's board authorized a quarterly payout of 21.25 cents per share, up from 16.25 cents per share.

WHY IT MATTERS: UnitedHealth, based in Minnetonka, Minn., is the largest U.S. health insurer and the first to announce earnings every quarter. Many analysts and investors see it as a bellwether for the managed care sector.

WellPoint, the second-largest insurer, reports its results July 25. Aetna Inc. follows on July 31, Cigna Corp. reports Aug. 2, and Humana Inc. releases results Aug. 6.

WHAT'S EXPECTED: Analysts surveyed by FactSet expect, on average, earnings of $1.18 per share on $27.36 billion in revenue.

LAST YEAR'S QUARTER: UnitedHealth's second-quarter earnings climbed 13 percent in 2011, as enrollment gains and slower-than expected growth in health care use helped the insurer. The company earned $1.27 billion, or $1.16 per share, as revenue rose 8 percent to $25.23 billion.