2017 was a whirlwind of a year for the property & casualtyinsurance sector. Extreme weather events — HurricaneHarvey, Irma, and Maria, along with extreme weather events inCalifornia, in particular — disrupted theindustry with record-breaking events.

Despite this, Fitch Ratings maintains a stable rating outlookfor a number of sectors. The rating agency compiled GAAP year-end financial results for 51property & casualty insurers and reinsurers that are publiclytraded or report GAAP consolidated reports. The group'scombined ratio rose to 102.0% in 2017 versus 96.8% in theprior year. Aggregate operating return on average equity (ROAE) in2017 declined to 4.6% from 6.5% in 2016.

Related: Lessons learned from a painful year ininsurance

Personal lines lead the pack

The personal lines group is the only subsegment to produce animproved calendar-year combined ratio in 2017, dropping to 94.6%from 96.2% in the prior year. Fitch credited Allstate Corp. andProgressive Corp., two of the largest members, with the group'spositive uptick.

Catastrophes in 2017 added 6.5 points to the personal segmentcombined ratio, up from 5.3 points in the prior year, with the 1.2point increase representing the smallest year-over-year change ofany segment.

Tax reform has mixed results

As a result of the recently enacted U.S. Tax Cut and Jobs Act,companies were required to evaluate their deferred tax asset (DTA)and liabilities (DTL) positions as of year-end 2017 and reporttheir corresponding impact into net earnings.

Of the 51 companies, 29 reported a one-time write-down of theirnet DTA positions, while the remaining 22 companies received abenefit from the revaluation of their net DTLs with the lower taxrate.

Fitch's “First Underwriting Loss in Six Years for P&CInsurers” special report is available at www.fitchratings.com.

Related: What We Know About Corporate Winners and Losers inTax Bill