Humana's purchase of OSF Health Plans will likely beef up the plan's presence in downstate Illinois, where Blue Cross Blue Shield and UnitedHealth dominate. Illinois health plans are adopting some aspects of value-based pharmacy design-which uses drug tiering and cost-sharing techniques to push members to the most cost-effective treatments rather than the cheapest drugs-as more research supports its cost-savings potential with certain drugs and conditions. Illinois is considering tax credits to encourage more wellness programs in the state. Illinois seniors are warming up to Medicare Advantage plans, particularly to the private-fee-for-service plans that have mushroomed across the state. Between December of 2007 and March 2008, enrollment is up 7.4 percent, with PFFS plan growth up 16 percent in the same period.