It depends on the state. You may be in a state with a special fund all physicians have to pay into to get a minimum malpractice coverage (usually 500k/1.5mil). In that case, your personal malpractice insurance picks up the rest (so in this case you might have an aggregate coverage of 1mil/3mil with half covered by the state and half covered by PMRS). I suspect this is the case because 1/3 is pretty standard.