An actuary is a health insurance carrier number cruncher responsible for determining what premiums the company needs to charge based in large part on claims paid versus amounts of premium generated. Their job is to make sure a block of business is priced to be profitable, but that the rates are also justified by claims costs (if the rates are too high, they could be rejected by state regulators, or the insurer will have to rebate excess premiums to members in the form of medical loss ratio rebates).