For the first time in a decade, the U.S. private auto insurance industry recorded a full-year underwriting profit in 2018.

According to an S&P Global Market Intelligence analysis, the average combined ratio in the space improved to 97.2% for the year from 102.2% in 2017. It was the first time the industry's combined ratio was below the 100% benchmark since 2008.

Market share rankings did not change much among the 20 largest personal auto insurers in 2018, as many companies recorded higher direct written premiums and lower combined ratios.

At the company level, only seven of the top 20 personal auto insurers recorded combined ratios above 100%. That represents a significant improvement from the previous year when only three of the top 20 companies posted underwriting profits. Sandler O'Neill & Partners analyst Paul Newsome in an interview said higher prices and better claim trends in 2018 led to the lower combined ratio figures.

Rate increases on existing books of business were the primary driver of premium growth in personal auto, CFRA analyst Cathy Seifert said in an interview.

Berkshire Hathaway Inc., mostly through its GEICO Corp. unit, and Progressive Corp. retained their respective No. 2 and 3 spots and were among the seven insurers in the top 20 that recorded double-digit percentage increases in direct premiums. Berkshire posted 11.8% year-over-year growth, while Progressive reported an 18.8% increase in written premiums.

"Progressive is a good example of a company that has benefited from an increase in rates, coupled with market share gains, and the company continues to have both underwriting and marketing platforms that are superior to peers," CFRA's Seifert said. "This makes it very easy for them to write new business and gain share from competitors."

State Farm Mutual Automobile Insurance Co., far and away the largest personal auto insurer in the U.S., reported a combined ratio of 97.1% and direct written premiums of $41.95 billion. Its growth rate, however, was fairly negligible as direct written premiums were up only 0.3% year over year.

Kemper Corp. moved up the rankings the most in 2018, jumping two spots to become the 13th-largest personal automobile underwriter, based on 2018 direct premiums written. The insurer posted a combined ratio of 98.6% and direct written premiums of $3.08 billion.

All the other companies in the list saw their direct premiums increase in 2018, except Nationwide Mutual Group and The Hartford Financial Services Group Inc., which saw their premiums fall by 8.4% and 8.6%, respectively.

S&P Global Market Intelligence offers a variety of tools to analyze underwriting performance of insurance companies. Click here for a template to review annual underwriting information and market share for P&C insurance companies by lines of business. This information is also available in the U.S. Insurance Statutory Financials database. Click here for an instructional webinar on how to operate the powerful P&C market share template, which allows detailed analysis by lines of business.