Table 4.

Sample Descriptive Statistics (N=38,185 observations, 21,965 persons) Statistics Listed Are: 1993 Average/1996 Average/Average over All Observations

HMO Member	Yes:	5%/ 22%/ 12%	Health Status:
			Self-perceived:	Excellent/very good:	42%/ 44%/ 42%
Sociodemographics:				Good/fair:	50%/ 49%/ 50%
Age	65–74:	40%/ 43%/ 40%		Poor:	8%/ 7%/ 8%
	75–84:	40%/ 40%/ 40%
	85+:	20%/ 17%/ 20%	ADLs:	Mean:	4.89 / 5.09 / 4.95 (s.d. 1.81 / 1.65 / 1.77)
Sex:	Male:	39%/ 41%/ 40%	IADLs:	Mean:	4.57 / 4.85 / 4.66 (s.d. 2.03 / 1.85 / 1.98)
Race:	White:	88%/ 88%/ 88%	Health limits social life:	Yes:	38%/ 32%/ 36%
	Black:	9%/ 9%/ 9%	Number of health	Mean:	2.98 / 2.82 / 3.00 (s.d. 2.06 / 2.00 / 2.07)
	Other:	3%/ 3%/ 3%	conditions (of 17):
Nursing home:	Yes:	10%/ 7%/ 9%	Arthritis:	Yes:	57%/ 54%/ 57%
Education:	<High school:	27%/ 23%/ 25%	Cancer:	Yes	20%/ 18%/ 20%
	High school:	45%/ 46%/ 46%	Stroke:	Yes:	13%/ 13%/ 14%
	Some college	25%/ 28%/ 26%	Other conditions (of 14):	Mean:	2.16 / 2.02 / 2/16 (s.d. 1.75 / 1.68 / 1.75)
			Market Characteristics:
	Missing:	3%/ 3%/ 3%	IPA model HMO in county:	Yes:	91%/ 98%/ 95%
Income:	<$10,000:$10,000–$30,000:	35%/ 25%/ 31%49%/ 49%/ 50%	Percent penetration:†	Mean:	4.99 / 13.80 / 9.00 (s.d. 9.55 / 14.74 / 12.80)
	$30,001–$50,000:	11%/ 13%/ 12%	Control variables:
	>$50,000:Missing:	5%/ 5%/ 5%0%/ 6%/ 2%	AAPCC rate:‡	Mean:	−45.59 / 48.18 / 3.41 (s.d. 82.32 / 104.87 / 101.68)
Medigap:	Yes:	67%/ 63%/ 65%	Year of observation:	1993:	N=7,810 (21%)
	No:	31%/ 37%/ 34%		1994:	N=8,528 (22%)
	Missing:	2%/ 0%/ 1%		1995:	N=8,474 (22%)
Medicaid:	Yes:	13%/ 11%/ 13%		1996:	N=13,373 (35%)
Usual source of care:	Yes:	87%/ 88%/ 88%

^†The relatively high HMO membership and mean penetration in 1996 reflects the MCBS's 1996 oversample of HMO enrollees

^‡Deviation from the mean