title: Health plan switching in anticipation of increased medical care utilization.
abstract: We compare rates and days of maternity and nonmaternity hospital admission for the years 1981 through 1984 for three groups of employees and dependents from a large private employer: those continuously enrolled in a fee-for-service (FFS) plan (N = 147,700), those continuously enrolled in a health maintenance organization (HMO) (N = 30,957), and those switching from the FFS plan to the HMO (N = 2,144). The rate of maternity admissions for plan switchers increased by 106% (P < 0.001) in the post-switch year compared with the pre-switch year, while maternity rates for continuing FFS-plan enrollees declined by 12% (P < 0.001) and rates for continuing HMO enrollees remained unchanged. Nonmaternity admission rates for switchers decreased by 19% (P = 0.079), consistent with the expectation that HMOs reduce these rates substantially, while rates for FFS-plan stayers increased 4% (P < 0.001) and those for HMO stayers remained unchanged. We conclude that employees often switch health plans when anticipating increased needs for maternity care and therefore that pre-switch rates of utilization are unreliable measures of the true magnitude of risk selection between HMOs and FFS plans.
authors.affiliation: School of Public Health, University of California, Berkeley.
authors.forename: J C
authors.initials: JC
authors.lastname: Robinson
authors.forename: L B
authors.initials: LB
authors.lastname: Gardner
authors.forename: H S
authors.initials: HS
authors.lastname: Luft
mesh_terms: D002140:California; D002755:Choice Behavior; D005251:Fees, Medical / Q000706:statistics & numerical data*; D005544:Forecasting; D006264:Health Benefit Plans, Employee / Q000706:statistics & numerical data*; D006279:Health Maintenance Organizations / Q000706:statistics & numerical data*; D006302:Health Services Research; D006771:Hospitals, Maternity / Q000191:economics / Q000706:statistics & numerical data*; D006801:Humans; D007342:Insurance Benefits / Q000592:standards*; D007344:Insurance Claim Reporting / Q000706:statistics & numerical data; D015273:Insurance Selection Bias; D007902:Length of Stay / Q000706:statistics & numerical data; D015233:Models, Statistical; D010343:Patient Admission / Q000706:statistics & numerical data*; D010351:Patient Discharge / Q000706:statistics & numerical data