Swiss Re Ltd. edged out Munich Reinsurance Co. to take the No. 1 position in A.M. Best Co. Inc.’s 2017 ranking of the top 50 global reinsurance groups, the rating agency said Thursday.

The change in top spot was the first for any of the top three spots in the annual ranking since 2010, Oldwick, New Jersey-based Best said in a statement, with Hannover Re S.E. continuing to rank No. 3. 

PartnerRe Ltd. and Everest Re Group Ltd. both fell out of the top 10, according to the new Best special report, “Down But Not Out: Reinsurers Look to Reposition Amid Market Disruption.” 

Best Senior Director Robert DeRose said the takeaway from the report is that “Swiss Re and Munich Re are the reinsurance market’s undisputed largest and most influential players.”

“Both have roughly double the premium volume of their closest competitors, offer similar capacity across nearly all reinsurance products and geographies and have been the market leaders for well over a decade,” Mr. DeRose said in a statement. “One is the immovable object, and the other is the unstoppable force; we will leave it to market participants and observers to decide which is which.”

The 2017 ranking is based on reinsurance gross premiums written, with the top 10 comprising about 70% of the top 50 total.

Under Best’s formula, if a company’s or group’s gross premiums written for reinsurance is 75% or more of its entire gross premium volume, all gross premiums written are counted in the ranking as reinsurance premiums. 

If a company’s or group’s reinsurance-to-insurance split consists of less than 75% reinsurance premiums, then just the reinsurance premiums are counted and the insurance premiums are excluded.

Since Munich Re’s significant primary operations account for just more than 30% of its total gross premiums written, its insurance premiums have been excluded, in line with Best’s approach. 

Swiss Re’s reinsurance-to-primary insurance split is more modest, with roughly 15% of gross premiums written coming from insurance operations, putting it under the threshold to split out its insurance and reinsurance premiums.

Everest Re’s ranking drop to 14 from nine was effected by Best’s approach, as its primary insurance premiums increased above the 25% threshold.

Moving up to the top 10 were Great West Lifeco and Korean Reinsurance Co., at No. 9 and No. 10 respectively. Most of the other changes in the ranking were due to ongoing merger and acquisition activity in the sector.

The top 50 reinsurance groups recorded an average combined ratio of 93.1% in 2016, which mirrored the average combined ratio of the top five reinsurers in the ranking and reflected the underwriting discipline employed by the industry, Best said.

This year’s report for the first time breaks out two subrankings of top nonlife and life global reinsurers. 

Although the growth in convergence capacity has slowed from previous years, it still grew by about 10%. Best estimates that alternative capital represents roughly $80 billion of capacity, with the vast majority of capital — $345 billion — coming from traditional sources.