The Dartmouth Atlas of Healthcare calculates preventable hospital admissions by considering the discharges for ambulatory care-sensitive conditions from short-stay acute care hospitals per 1,000 medicare enrollees. This is measured as a 5-year average and is adjusted for age, sex, and race. For more information, see Regional and Racial Variation in Primary Care and the Quality of Care among Medicare Beneficiaries (2010) (https://www.dartmouthatlas.org/downloads/reports/Primary_care_report_090910.pdf).