Some give all the credit to Obamacare. Others cite the poor economy or employers forcing workers to bear more of the cost of their medical expenses. Whatever the reason, health-cost increases stayed tame through the first half of the year, insurers say. Thursday's report from Cigna was the last dispatch on second-quarter financial results from major medical carriers. Cigna's results were similar to those of its rivals: higher-than-expected profits thanks largely to moderate increases in medical prices and the number of medical procedures.