Algunas marcas e indicadores en la ironía

Eligibility /10 -0.025 -0.116 -0.010 -0.029 0.003 -0.029 (0.056) (0.123) (0.019) (0.033) (0.019) (0.034) Fee Ratio 1.090 0.474 0.356 0.151 0.358 0.151 (0.196) (0.620) (0.059) (0.173) (0.059) (0.174) N 1602 1555 1602 1602 1602 1602 R / Pseudo R2 2 0.037 0.093 0.045 0.119 0.044 0.119

State Dummies No Yes No Yes No Yes

Note: Huber-White standard errors in parentheses. The dependent variable is a 0-1 indicator of physician participation in Medicaid. Models also control for physician age, sex, race, specialty, and year.

Dependent Variable: Percent of Practice Medicaid* OLS OLS IV IV (1) (2) (3) (4) Eligibility /10 0.995 -0.216 1.217 -0.556 (0.685) (1.212) (0.684) (1.219) Eligibility /10*Public 7.774 8.196 7.529 8.000 (1.334) (1.336) (1.324) (1.323) Fee Ratio 5.301 7.766 5.286 7.989 (1.835) (5.471) (1.833) (5.497) Fee Ratio*Public -48.811 -49.474 -48.540 -49.277 (7.916) (7.533) (7.900) (7.515) N 1897 1897 1897 1897 R2 0.210 0.244 0.210 0.244

State Dummies No Yes No Yes

Note: Huber-White standard errors in parentheses. The dependent variable is the percent of patients covered by Medicaid. IV models are estimated with instrumental variables using simulated eligibility as an instrument for actual eligibility.

Dependent Variable: Percent of Practice Medicaid*

Alternate Additional Add Add Add Use Fee Physician HMO Market Area Physicians Ob/Gyns Ratio Controls Share Characteristics Per Capita Only

(1) (2) (3) (4) (5) (6)

Eligibility/10 -0.547 -0.585 -0.822 -0.887 -0.649 -2.645 (1.234) (1.235) (1.217) (1.199) (1.224) (3.549) Eligibility/10*Public 5.562 7.934 7.525 7.856 7.795 8.439

(1.367) (1.329) (1.350) (1.343) (1.348) (4.586) Delivery Fee Ratio --- 7.704 7.324 3.995 6.355 23.219

(5.509) (5.419) (5.446) (5.539) (14.344) Delivery Fee Ratio* Public --- -49.728 -49.367 -48.873 -49.210 -69.109

(7.695) (7.705) (7.657) (7.810) (26.566)

Alternate Fee Ratio 6.195 --- --- --- --- ---

(3.205)

Alt. Fee Ratio*Public -30.283 --- --- --- --- --- (5.364) Lower-Middle Class --- 0.292 --- --- --- --- (1.753) Middle Class --- -0.170 --- --- --- --- (1.324) Upper-Middle Class --- 0.024 --- --- --- --- (1.596) Upper Class --- 2.275 --- --- --- --- (1.845)

U.S. Born IMG --- -0.359 --- --- --- ---

(1.614)

Non-U.S. Born IMG --- 1.560 --- --- --- ---

(1.659)

HMO Market Share --- --- -31.088 --- --- ---

(4.919) % Pop Female --- --- --- 0.230 --- --- (0.456) % Pop Non-White --- --- --- -0.031 --- --- (0.041) % Pop Over 65 --- --- --- 0.148 --- --- (0.139)

Per Capita Income --- --- --- -0.001 --- ---

(0.000)

Unemployment Rate --- --- --- 1.261 --- ---

(0.240)

Physicians Per Capita --- --- --- --- -842.808 --- (273.961)

N 1897 1886 1864 1864 1864 376

R2 0.243 0.246 0.259 0.285 0.247 0.312

State Dummies Yes Yes Yes Yes Yes Yes

Note: Huber-White standard errors in parentheses. The dependent variable is the percent of patients covered by Medicaid. All models are estimated using instrumental variables. The models also control for physician age, sex, race, setting group, specialty, and year. The sample sizes for some of these specifications are slightly smaller than the sample sizes in the main models because the necessary additional information was not available for all physicians. IMG stands for International Medical Graduate, and denotes physicians who graduated from medical schools located outside of the United States.

Information in this appendix is drawn primarily from Yelowitz, 1995 and Coughlin et al., 1994. 1

DEFRA 1984 (Deficit Reduction Act of 1984; P.L. 98-369): Required coverage for pregnant women provided that they would qualify for AFDC or AFDC-Unemployed Parent once the child was born.

COBRA 1985 (Consolidated Omnibus Budget Reconciliation Act of 1985; Pl. 99-272): Required coverage for pregnant women if family income and resources are below state AFDC levels, regardless of family structure. Required 60-day postpartum extension of coverage for women eligible because of pregnancy.

OBRA 1986 (Omnibus Budget Reconciliation Act of 1986; P.L. 99-509): Allowed states to extend Medicaid coverage to pregnant women, infants, and children under age 2 who have incomes below 100% of the Federal poverty level (created new optional categorically needy group), effective April 1987. Authorized states to guarantee continuous eligibility through postpartum period for women covered for pregnancy.

OBRA 1987 (Omnibus Budget Reconciliation Act of 1987; P.L. 100-203): Allowed states to cover pregnant women and infants with incomes below 185% of Federal poverty level.

MCCA 1988 (Medicare Catastrophic Coverage Act of 1988; P.L. 100-360): Required states to cover pregnant women and infants on a phased-in schedule: to 75% of the Federal poverty level effective July 1989 and to 100% of the Federal poverty level effective July 1990.

FSA 1988 (Family Support Act of 1988; P.L. 100-485): Required coverage for AFDC-eligible families with unemployed parent. Effective April 1990, required states to continue Medicaid coverage for 12 months to families under 185% of Federal poverty level who had received AFDC in the 3 of the previous 6 months, but who became ineligible because of increased earnings.

OBRA 1989 (Omnibus Budget Reconciliation Act of 1989; P.L. 101-239): Effective April 1990, required coverage for pregnant women, infants, and children with incomes below 133% of the Federal poverty level. Encouraged states to increase fees for obstetric procedures.

OBRA 1990 (Omnibus Budget Reconciliation Act of 1990; P.L. 101-508): Required continuous eligibility through postpartum period for women covered for pregnancy.

(1&D_{)P rn} ' 1&N N DP rm 1 D&1 ' 1&N N r_m r_n D ' 1&N N r_m r_n % 1 &1 . ˆ D_i ' 1&Ni N_i Rˆi % 1 &1 N N (A-3) (A-4) (A-5) (A-6) The 1991 SYP asked physicians to report the percent of their practice revenues that were obtained from Medicaid. We use this data to estimate the percent of their patients covered by Medicaid. To do this, we first related the percent of patients in a representative practice covered by Medicaid, which we denote D, to the percent of revenues in the practice from Medicaid, denoted N. We know:

DP rm = T (A-1)

(1-D) P r n = (1- )T (A-2)

where P denotes the number of patients in the practice, rm and rn denote the average revenue derived from Medicaid and non-Medicaid patients, respectively, and T denotes total practice revenues.

Combining equations (A-1) and (A-2) yields

which implies

so that we have

Using the reported percent revenue from Medicaid N and an estimate of the revenue ratio rm/ rn for each physician i in 1991, we use equation (A-5) to generate an estimate of the percent of patients covered by Medicaid:

where R denotes the ratio of Medicaid to non-Medicaid revenues. To estimate the revenue ratio for each physician, we use a state-specific weighted average of the ratio of Medicaid to private charges for 15 common primary care procedures (Holahan, 1991). The weights are the proportion of Medicaid expenditures for each of the 15 services. It is likely that private charges overstate the actual payments that physicians receive for these services. An AMA study reported that in 1985 physicians faced, on average, 7 percent discounting from traditional insurers, 11 percent discounting from PPOs, and 17 percent discounting from IPAs (AMA,

1991, we used a factor of 20% for discounting, reducing private charges by 20% in our calculations. To test the robustness of our finding to variations in the revenue ratio used to transform the 1991 percent revenues variable, we also experimented with a variety of additional revenue ratio estimates including holding the ratio fixed at 1 for all physicians (so that D = N ), using a weighted average of the ratio of

Medicaid to private fees for 4 obstetrical procedures (Holahan, 1991), and assuming 0, 10, and 30 percent discounting for private fees. In no case did these modifications alter our conclusions.

To examine the reliability of physician reports about the percent of their patients covered by Medicaid, and the reliability of our estimation procedure for the 1991 physicians, we obtained comparison data from the 1985 and 1991 National Ambulatory Medical Care Surveys (1985 and 1991 NAMCS). No NAMCS data are available from 1987; 1985 is the closest year available. We used these surveys to compute the percentage of office visits to private physicians in general practice, family practice, general internal medicine, and obstetrics and gynecology that were made by patients with Medicaid coverage. We compare these percentages to the (weighted) mean percent of patients from Medicaid among our office-based

physicians. On the 1985 NAMCS, 9% of visits were covered by Medicaid, while the 1987 SYP data implies that 13% of visits were Medicaid-covered. On the 1991 NAMCS, 10% of visits were covered by Medicaid and the 1991 SYP data imply that 16% of visits were covered by Medicaid. Given evidence from

comparisons of the SYP and a sample of older physicians drawn from the American Medical Association's 1991 Socioeconomic Monitoring System survey (a random sample of all physicians in the U.S.) showing that younger physicians are generally more likely to treat Medicaid patients than older physicians (and the

NAMCS represents all physicians, not just young ones), these results suggest that physician reports of their Medicaid service, and the method we use to estimate the percent of Medicaid patients for 1991 SYP physicians, are in line with data from other sources.

We made similar comparisons for public physicians using data from the 1992 National Hospital Ambulatory Medical Care Survey (NHAMCS), which contains data on the insurance coverage of patients seen in hospital outpatient departments and emergency departments. (These data are not available for other years.) Again, the percent of visits covered by Medicaid implied by the SYP data are somewhat higher than the percent shown by the NHAMCS--the NHAMCS data indicate that 29% of visits were made by patients covered by Medicaid, while the 1991 SYP data indicate that 34% of visits to public physicians were made by patients covered by Medicaid. But, as above, since the universe of physicians is not precisely the same in the two surveys, we interpret this comparison as consistent with the validity of physician reports and our

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