The health insurance companies collect money monthly from all enrolled participants. That money sits on their books until it has to be paid out for claims. High

The health insurance companies collect money monthly from all enrolled participants. That money sits on their books until it has to be paid out for claims. Higher healthcare costs means that the insurance company can raise the monthly premiums, which means that it's got more money sitting in it's accounts before the claims get paid. That money isn't under a mattress; the insurance company has it invested in something that's earning interest. So higher healthcare costs == more interest earned on the premiums as they pass through the insurance company on the way to paying claims.