If the largest healthcare insurer in the U.S. leaves Obamacare entirely, it would cause premiums to rise as much as $100 and would reduce competition, a new analysis found.

The analysis from the nonprofit Kaiser Family Foundation comes as UnitedHealth, the country’s largest insurer, is fleeing Obamacare markets in Georgia, Arkansas and Michigan starting next year. UnitedHealth has previously considered leaving all Obamacare exchanges due to losses of $425 million last year, and other insurers have had problems reaching profitability in Obamacare.