The flurry of insurance mergers and acquisitions that yielded about $150 billion of transactions globally in 2015 may endure even after years of “patchy” results for some companies making deals, according to ratings firm Standard & Poor’s.

“We believe the deal flow for M&A in the insurance industry will continue in 2016, albeit more slowly,” Standard & Poor’s analysts led by Dennis Sugrue said Monday in a report. “While a successful M&A can benefit the surviving entity, the general consensus is that its track record is not great.”

Among last year’s biggest deals were Ace Ltd.’s agreement to purchase Chubb Corp. for more than $28 billion and Exor SpA’s announcement that it would acquire reinsurer PartnerRe Ltd. for more than $6 billion. Insurers have struggled in recent years to create value amid the glut of transactions, S&P said.

“Over two-thirds of M&A deals since 2000 failed to improve financial strength enough to lead us to upgrade the buyer,” the analysts said. “We take a conservative view on M&A for rated insurers, and we place a heavy emphasis on the risks.”

Different classes of buyers entered the arena, including corporate conglomerates and sovereign wealth funds, the ratings firm said. Asian insurers sought deals in the U.S. last year as growth slowed at home. Japan’s Sumitomo Life Insurance Co. agreed in August to buy Symetra Financial Corp. for about $3.8 billion, while China’s Anbang Insurance Group Co. said in November it would purchase U.S. insurer Fidelity & Guaranty Life.