[1] Res Triangle Inst, Hlth & Social Policy Div, Washington, DC 20036 USA
[2] Penn State Univ, Dept Hlth Policy & Adm, University Pk, PA 16802 USA
[3] Rand Corp, Santa Monica, CA USA
[4] US Dept HHS, Agcy Hlth Care Policy & Res, Ctr Org & Delivery Studies, Rockville, MD 20852 USA
[5] Univ Massachusetts, Survey Res Ctr, Boston, MA 02125 USA