Table 5.
Linear Probability (Ordinary Least Squares) and IV Estimates of the Effect of “For-Profit” Status of Initial Dialysis Center on 1-Year Survival, 1996–1999
| Estimation Method and Specification | Number of Patient Groups Specified Using Differential Distance | Instrument Group Partial F-Statistic (p-Value) | Hausman F-Statistic (p-Value) | Estimated Effect (Std Error, p-Value) |
|---|---|---|---|---|
| LPM; no covariates | NA | NA | NA | −0.0031 (0.00328; .3450) |
| LPM; Devereaux covariates* | NA | NA | NA | −0.01221 (.00319;<.0001) |
| LPM; Devereaux covariates plus† | NA | NA | NA | −0.00715 (0.00366; .0511) |
| LPM; Devereaux covariates plus† without state dummies | NA | NA | NA | −0.01315 (0.00321;<.0001) |
| LPM; Devereaux covariates plus† without previous health care utilization | NA | NA | NA | −0.00759 (0.00368; .0395) |
| LPM; Devereaux covariates plus† without zip code socioeconomic variables | NA | NA | NA | −0.00726 (0.00366;0.0475) |
| LPM; Devereaux covariates plus† without distance to nearest dialysis center | NA | NA | NA | −00702 (0.00366; .0554) |
| 2SLS† | 2 | 18535.00 (<.0001) | NA | 0.00072 (0.00933; .939) |
| 2SLS† | 5 | 7909.59 (<.0001) | 0.64 (0.5877) | 0.00248 (0.00754; .746) |
| 2SLS† | 10 | 3991.69 (<.0001) | 0.99 (0.4379) | −0.00012 (0.00719; .986) |
| 2SLS† | 20 | 2150.53 (<.0001) | 0.82 (0.6625) | −0.00024 (0.007151; .973) |
| 2SLS† | 40 | 1003.79 (<.0001) | 1.23 (0.1583) | 0.00049 (0.007113; .945) |
*
Also specified patient age, gender, comorbidity, and race.
†
Also specified patient age, gender, comorbidity, race, state of residence, number of inpatient admissions and inpatient days in the year prior to dialysis, zip code-level measures of poverty, per capita income, and percent rural, distance to nearest dialysis center.
LPM, linear probability model; 2SLS, two-stage least squares.