Exhibit 4. PGP Demonstration Impacts on Utilization: Absolute Difference-in-Differences Demonstration Effects.

	Hospitalizations				Emergency Department Visits
PGP	Mean Hospitalizations	Probability> 0	Number,Given > 0	Total Effect	Mean visits	Probability> 0	Number,Given > 0	Total Effect
Pooled	0.364	-0.0048***	-0.0056*	-0.0089***	0.633	-0.0060***	-0.0086	-0.0137***
1	0.315	0.0051*	0.0044	0.0086	0.690	-0.0034	0.0195	0.0047
2	0.357	-0.0097***	-0.0193	-0.0208***	0.544	-0.0048*	0.0125	-0.0011
3	0.306	-0.0051	-0.0112	-0.0110*	0.589	0.0093**	0.0269	0.0275
4	0.382	0.0023	-0.0120	-0.0022	0.679	0.0068*	-0.0054	0.0085
5	0.406	-0.0063***	0.0015	-0.0085*	0.657	-0.0093***	-0.0001	-0.0138
6	0.330	-0.0148***	-0.0330***	-0.0335***	0.665	-0.0193***	-0.0472***	-0.0523***
7	0.350	-0.0031	0.0158	0.0026	0.543	-0.0109***	-0.0377*	-0.0355***
8	0.372	-0.0081***	0.0190*	-0.0023	0.560	-0.0024	0.0204	0.0055
9	0.359	0.0016	-0.0035	0.0001	0.676	-0.0049*	-0.0080	-0.0122
10	0.454	0.0005	0.0123	0.0072	0.720	-0.0049*	-0.0107	-0.0105

¹NOTES: Probabilities of at least one hospitalization and of at least one Emergency Department visit were estimated using logit regression models.

²Number of hospitalizations conditional on at least one hospitalization and number of ED visits conditional on at least one visit were estimated with zero-truncated negative binomial models.

³Logistic and negative binomial regression models included demographic and geographic covariates, pre-existing trends, and the risk score.

⁴Regression estimates are weighted by each person/year’s inverse propensity score and the fraction of each year eligible for Medicare.

^***= significant at 1% level;

^**= significant at 5% level;

^*= significant at 10% level.

SOURCE: Authors’ analysis of Medicare claims and enrollment data for 2001 to 2010.