A sharp increase in direct premiums pushed Berkshire Hathaway Inc. up the rankings to become the fifth-largest U.S. excess and surplus line writer as of year end 2017.

According to an analysis of statutory data, Berkshire at the end of 2017 had a 4.8% share of the market and saw its direct premiums grow by 27.0% year over year.

Berkshire Hathaway grew its direct premiums written to $1.50 billion from $1.18 billion in 2016, when Berkshire was ranked eighth in the U.S. E&S market. The group's specialty insurance underwriter, National Fire & Marine Insurance Co., wrote 78% of the group's E&S premiums in 2017. Its premiums jumped by 30.82% from the prior year. At the individual company level, this unit of Berkshire ranked fourth nationally with $1.18 billion in direct premiums written in 2017.

American International Group Inc. remains the largest E&S writer in the country but is continuing to lose market share to rivals. AIG's year-over-year premiums declined 16% in 2017, and the company now only has about 10.25% of the total U.S. E&S market. During a fourth-quarter 2017 earnings call, AIG executives said the recently announced deal for Validus Holdings Ltd. would bring in a valuable complementary business and allow AIG to expand its capabilities in various business lines, including commercial E&S.

Among the top E&S writers, W. R. Berkley Corp., Nationwide Mutual Group lost market share by 38 and 27 basis points, respectively. Their rankings remained unchanged on a year-over-year basis.

Overall, the U.S. E&S market saw direct premiums written increase by 5.40% in 2017.

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