Exhibit 3.
Average annual change in risk-adjusted regional spending deviation within ACO cohorts attributable to participation changes before and after the introduction of regionalized benchmarks, measured by ACO subgroups
| Mean annual within-cohort change in risk-adjusted regional spending deviation, $ per beneficiary-year (SE) | ||
|---|---|---|
|
| ||
| During Pre-Benchmark Regionalization
Period 2013 – 2016 |
During Post-Benchmark Regionalization
Period 2017 – 2019 |
|
|
| ||
| Changes due to ACO-level exit or within-ACO reconfiguration | ||
| By ACO’s size at entry (number of beneficiaries) | ||
| Small (less than 1,500) | −8.52 (9.02) | −9.87 (6.54) |
| Medium (1,500 to 3,500) | 17.73 (5.52)* | −19.25 (4.03)* |
| Large (more than 3,500) | 5.39 (3.65) | −17.49 (2.91)* |
| By convener involvement | ||
| Convener-involved | −13.30 (10.74) | −76.04 (8.80)* |
| Non-convener | 12.66 (3.11)* | −16.40 (2.32)* |
| By distribution of beneficiaries within the ACO at entry | ||
| Concentrated | 9.93 (3.63) | −8.55 (2.42)* |
| Dispersed | 6.18 (4.74) | −28.23 (4.26)* |
| By convener involvement * beneficiary distribution | ||
| Convener + concentrated | −8.45 (13.08) | −41.48 (10.35)* |
| Convener + dispersed | −8.35 (14.43) | −103.87 (13.10)* |
| Non-convener + concentrated | 11.50 (3.75)* | −8.28 (2.41)* |
| Non-convener + dispersed | 10.07 (5.07) | −16.56 (4.59)* |
| Changes due to within-ACO reconfiguration only | ||
| By ACO’s size at entry (number of beneficiaries) | ||
| Small (less than 1,500) | 2.19 (8.19) | 5.37 (5.72) |
| Medium (1,500 to 3,500) | 5.36 (4.65) | −11.42 (3.17)* |
| Large (more than 3,500) | 9.11 (3.51) | −17.13 (2.42)* |
| By convener involvement | ||
| Convener-involved | 11.90 (9.32) | −10.57 (7.15) |
| Non-convener | 5.27 (2.87) | −14.07 (1.96)* |
| By distribution of beneficiaries within the ACO at entry | ||
| Concentrated | −4.21 (3.17) | −4.59 (1.96) |
| Dispersed | 12.69 (4.42)* | −17.59 (3.43)* |
| By convener involvement * beneficiary distribution | ||
| Convener + concentrated | −15.66 (11.11) | 2.45 (7.56) |
| Convener + dispersed | 22.39 (12.33) | −24.92 (10.35) |
| Non-convener + concentrated | −3.55 (3.28) | −5.55 (1.96) |
| Non-convener + dispersed | 9.61 (4.84) | −20.26 (3.70)* |
SOURCE Authors’ analysis of CMS MSSP Provider-level Research Identifiable Files, Medicare claims, and MD-PPAS data.
NOTES:
p<0.0045 based on two-sided z-test using bootstrapped standard errors (null hypothesis of zero average change) and after applying Bonferroni correction for multiple comparisons within column and panel (for family-wise p<0.05); Means are weighted by number of attributed beneficiaries and based on study ACOs that entered the Medicare Shared Savings Program prior to benchmarking changes (i.e., cohorts 2012 through 2016); Net changes due to within-ACO participant list reconfiguration only were estimated among the subset of ACOs participating in the MSSP in the following year (see Appendix for details); If ACOs never exited and never changed their participant list from their initial entry through 2019, all values above would equal zero; ACO size represents the number of attributed beneficiaries based on the study’s 20% sample; Concentrated ACOs are defined as those where the Herfindahl-Hirschman Index (HHI), based on shares of attributed beneficiaries across tax identifier number (TIN) or CMS certification number (CCN), is ≥2,500.