Table 1.

Descriptive Statistics of Model Variables in Selected Years for the Enrollment History Groups^*

	Enrollment History Groups
	1992–1993 HMO Switchers		Continuous HMO
Model Variables	Group/Staff	IPA	Group/Staff	IPA	Continuous FFS
Dependent Variables (Mean)
Admissions/beneficiary
1991	.18	.14	.16	.14	.23
1995	.29	.25	.24	.22	.33
Total inpatient d/y
1991	1.05	.82	.75	.71	1.49
1995	1.41	1.17	1.05	.92	1.96
Part I: Probability of one stay of at least one d/y
1991	.12	.11	.11	.11	.15
1995	.18	.16	.15	.15	.20
Part II: Log (inpatient d/y given one stay of at least one day)
1991	1.73	1.64	1.52	1.50	1.83
1995	1.62	1.54	1.50	1.37	1.80
Independent Variables (Mean)
Proportion of year in HMO (HMO Effect)
1991	0	0	1	1	0
1995	.92†	.94†	1	1	0
Other Independent Variables (Percentage in 1991)‡
Male	43.2	42.3	43.7	41.8	39.5
African American	7.9	2.8	7.9	1.6	4.1
Medicaid-eligible	11.3	4.9	5.3	2.7	18.9
Disabled, >64 years	7.4	6.2	5.9	5.7	7.2
Age, years
65–69	33.0	30.2	31.9	25.5	25.1
70–74	28.6	30.4	30.5	31.3	27.8
75–79	19.3	20.6	20.1	22.2	21.0
80–84	11.6	11.6	10.8	12.7	13.9
85+	7.5	7.2	6.7	8.3	12.2
Death from ’93 through ’96	18.5	16.5	17.5	17.4	24.7
No. of Beneficiaries in 1991	39,383	84,728	10,861	7,415	108,966

^*HMO indicates health maintenance organization and FFS indicates fee-for-service.

^†Less than 100 percent because of disenrollment to FFS. Over the course of the study 8.6 percent of the beneficiaries who joined either a group/staff or IPA HMO in 1992 or 1993 disenrolled to FFS. This variable is 0 for those who disenrolled before 1995 and between 0 and 1 for those disenrolling in 1995.

^‡The number of beneficiaries will change over time due to deaths and therefore so will the percentage. All percentages refer to 1991 except death.