aged (Conventional + HMO) % of All Healthcare Plans Other (HDHP) 0% T T T T T T T T T T T T T T 1 1988 1996 2000 2002 2004 2006 2008 Note: PPO is Preferred Provider Organization, which allows enrollees to select any doctor / hospital in the insurance provider's network without going through a primary care physician. HMO is H