Table 4.
Alternate Specifications
| % Received Intensive Treatment | % Treated within 1 Day | Average No. of Procedures | % Die in Hospital | Average Length of Stay | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
| (1) | (2) | (3) | (4) | (5) | (6) | (7) | (8) | (9) | (10) | |
| Panel 1: IV with HHI; without hospital referral region time trends | ||||||||||
| Merged share | 0.037 (0.012)*** | 0.023 (0.010)** | 0.086 (0.029)*** | 0.065 (0.028)** | 0.332 (0.171)* | 0.167 (0.169) | 0.009 (0.003)*** | 0.006 (0.002)*** | 0.322 (0.225) | 0.198 (0.206) |
| HHI | 0.045 (0.077) | 0.136 (0.070)* | 0.163 (0.179) | 0.317 (0.200) | 1.853 (0.925)** | 2.772 (1.054)*** | −0.013 (0.015) | −0.020 (0.015) | 0.055 (1.025) | −0.024 (0.951) |
| R2 | 0.60 | 0.68 | 0.47 | 0.49 | 0.46 | 0.49 | 0.11 | 0.16 | 0.69 | 0.69 |
| Panel 2: IV with HHI; with hospital referral region time trends | ||||||||||
| Merged share | 0.056 (0.015)*** | 0.040 (0.013)*** | −0.052 (0.033) | −0.067 (0.034)* | −0.106 (0.185) | −0.207 (0.190) | 0.005 (0.003) | 0.007 (0.003)** | 0.396 (0.238)* | 0.321 (0.218) |
| HHI | −0.061 (0.079) | 0.053 (0.068) | 0.438 (0.171)** | 0.563 (0.186)*** | 2.703 (0.786)*** | 3.298 (0.843)*** | 0.000 (0.016) | −0.020 (0.016) | 0.096 (1.039) | −0.118 (0.983) |
| R2 | 0.61 | 0.70 | 0.47 | 0.49 | 0.49 | 0.52 | 0.11 | 0.16 | 0.69 | 0.70 |
| Observations | 47,396 | 47,396 | 47,396 | 47,396 | 47,396 | 47,396 | 47,396 | 47,396 | 47,396 | 47,396 |
| Panel 3: Hospital-level without hospital-specific time trends | ||||||||||
| Merged share | 0.058 (0.024)** | 0.059 (0.020)*** | 0.032 (0.015)** | 0.029 (0.015)* | 0.378 (0.191)** | 0.371 (0.189)* | −0.001 (0.003) | −0.001 (0.003) | 0.250 (0.185) | 0.265 (0.171) |
| R2 | 0.22 | 0.33 | 0.04 | 0.08 | 0.16 | 0.23 | 0.01 | 0.06 | 0.09 | 0.12 |
| Panel 4: Hospital-level with hospital-specific time trends | ||||||||||
| Merged share | 0.016 (0.021) | 0.021 (0.019) | 0.004 (0.014) | 0.006 (0.014) | 0.087 (0.157) | 0.122 (0.153) | 0.000 (0.003) | 0.000 (0.003) | 0.094 (0.148) | 0.186 (0.138) |
| R2 | 0.23 | 0.34 | 0.05 | 0.09 | 0.18 | 0.25 | 0.01 | 0.06 | 0.14 | 0.16 |
| Observations | 203,139 | 203,139 | 146,765 | 146,765 | 203,139 | 203,139 | 203,139 | 203,139 | 200,296 | 200,296 |
| Control variables | X | X | X | X | X | |||||
Notes. Robust standard errors in parentheses.
Significant at 10%;
Significant at 5%;
Significant at 1%.
All regressions include quarter and zip code or hospital fixed effects as applicable. Because satellite facilities cannot be tracked separately from the parent postmerger, facility pairs that merge in future are treated as a single facility for fixed effect purposes. Standard errors are clustered by zip code or hospital as applicable. Control variables include the percentage of discharges with demographic characteristics such as race, gender, and age categories; with expected payer such as Medicare and private insurance; with comorbidities such as hypertension, diabetes, and heart failure; admission through the ER; and a constant.