U.S. property/casualty insurers’ operating performance remained largely unchanged in the first half of 2015 compared to the same period a year prior, with $25.5 billion in aggregate operating earnings reported in both periods, according to a new report by Fitch Ratings.

Favorable reserve development and limited catastrophic loss activity helped to offset sluggish investment income, Fitch said in the report, “U.S. Property/Casualty Insurers’ Midyear 2015 Financial Results.”

Annualized operating ROAE (return on average equity) dropped slightly to 8.1 percent from 8.4 percent in 2014 due to modest growth in shareholders’ equity. The net income ROAE for the group declined more significantly to 8.6 percent versus 10 percent in first-half 2014 due to a reduction in realized investment gains

Underwriting performance remains favorable, Fitch said, as the group calendar-year combined ratio equaled the prior-year measure of 94.2 percent. However, the ratings agency warned that maintaining or improving underwriting performance going forward may prove challenging as competitive forces are promoting flat to declining insurance pricing in many segments.

Generating an operating ROAE above 10 percent remains a challenge in the current marketplace, Fitch said in the report, adding that only one-third of the companies in the group reported a double-digit operating ROE in first-half 2015.