Source
RTI International, 3040 Cornwallis Rd., PO Box 12194, Research Triangle Park, NC 27709-2194, USA.
Abstract
OBJECTIVE:
To investigate the use of regression models to calculate disease-specific shares of medical expenditures.
DATA SOURCES/STUDY SETTING:
Medical Expenditure Panel Survey (MEPS), 2000-2003.
STUDY DESIGN:
Theoretical investigation and secondary data analysis.
DATA COLLECTION/EXTRACTION METHODS:
Condition files used to define the presence of 10 medical conditions.
PRINCIPAL FINDINGS:
Incremental effects of conditions on expenditures, expressed as a fraction of total expenditures, cannot generally be interpreted as shares. When the presence of one condition increases treatment costs for another condition, summing condition-specific shares leads to double-counting of expenditures.
CONCLUSIONS:
Condition-specific shares generated from multiplicative models should not be summed. We provide an algorithm that allows estimates based on these models to be interpreted as shares and summed across conditions.