Exhibit 4.

Differential changes in acute hospital utilization and price-standardized hospital spending in the intervention and control populations

Outcome	Intervention population pre-period mean a	Adjusted changes between the pre- and post-intervention periods b		Adjusted differential change c
		Intervention population	Control population	Estimate	95% CI
Acute hospital utilization:
Acute hospital use (Hospital stays d and Emergency Department visits e; Annual Count/Beneficiary)	0.737	-0.007	-0.021	0.014	(-0.007 to 0.036)
Hospital stays (Annual Count/Beneficiary)	0.391	-0.078	-0.072	-0.006	(-0.020 to 0.007)
Emergency Department visits (Annual Count/Beneficiary)	0.346	0.071	0.051	0.020	(0.004 to 0.036)
30-day return acute hospital visits (Proportion) f	0.271	-0.014	-0.014	0.000	(-0.007 to 0.007)
Price-standardized hospital spending:
Acute hospital spending g (Hospital stay and Emergency Department spending; Annual $/Beneficiary)	4185	-1115	-1213	98	(-69 to 265)
Hospital Stay spending (Annual $/Beneficiary	4123	-1152	-1246	94	(-72 to 260)
Emergency department spending (Annual $/Beneficiary)	62	37	33	4	(-2 to 10)
Hospital Outpatient Department spending (Annual $/Beneficiary) h	618	393	450	-57	(-99 to -15)

^aUnadjusted annual mean in the intervention population over the period 2007-2009.

^bWe defined the pre-intervention period as the years 2007-2009 and the post-intervention period as the years 2011-2013. Because Maryland’s global budget program for rural hospitals was implemented in July 2010, we omitted 2010 from our regression analyses.

^cAdjusted differential change from the pre-intervention to the post-intervention periods, comparing Medicare beneficiaries in the intervention versus control populations. The differential change was estimated using a weighted patient- and year-level linear regression model, adjusted for patient characteristics as well as year and ZIP code fixed effects. The weights balance the observed characteristics of patients in the intervention and control populations in each study year (see Section 5 of the Appendix for details of our statistical methods).

^dHospital stays include inpatient admissions and observation stays.

^eEmergency department visits that did not lead to an inpatient admission.

^fAnnual proportion of patients’ inpatient admissions, observation stays, and emergency department visits followed within 30 days by a second inpatient, emergency department, or observation visit. Assessed annually among patients with ≥1 inpatient admission, emergency department visit, or observation stay during the study year.

^gBecause hospital prices were subject to change under Maryland’s global budget program, we price-standardized spending by applying mean national prices (measured annually at the level of Diagnosis-Related Groups for inpatient claims, revenue codes for observation-unit claims, and procedure codes for non-admitted emergency department claims) to claims for the corresponding categories of acute hospital use. Mean prices were calculated annually using Medicare claims from hospitals outside of Maryland.

^hWe price-standardized spending for hospital outpatient department services, excluding emergency department visits and observation stays, by applying national average procedure code-level prices to hospital outpatient department claims. Standardized prices were assessed annually from national Medicare claims, excluding hospitals in Maryland.

Source: Authors’ analyses of fee-for-service Medicare claims for the periods 2007-2009 and 2011-2013.