There's a new defection from Illinois' Affordable Care Act health insurance exchange. Aetna has announced it's leaving next year, increasing concerns about reduced competition. Six companies will remain that sell plans for next year to individuals and families on the Illinois "Obamacare" marketplace. UnitedHealthcare previously announced it was leaving the exchange. Land of Lincoln Health is shutting down entirely. Aetna reports higher than expected costs, especially costly specialty drugs, spurred their decision to leave.