UnitedHealth Group Incorporated occupied the top spot in AM Best's ranking of the world's 25 largest insurance companies for a fourth straight year, with $158.5bn in net premiums written (NPW) in 2017. In addition, Allianz SE moved up two places to the No. 1 spot on AM Best's ranking by 2017 non-banking assets, dislodging MetLife Inc., which fell to No. 5.