Table III.

Robustness checks on difference-in-difference estimates

DID estimate	Total volume	Services of specific category (% of total volume)
		Diagnosis	Examination	Radiology	Therapy	Surgery	Drug
	(1)	(2)	(3)	(4)	(5)	(6)	(7)
A. DID, hospital FEs	132.9*** (31.3)	−0.01631*** (0.00408)	−0.00406 (0.00422)	0.00521** (0.00249)	0.01217 (0.01477)	−0.02528*** (0.00837)	0.01113* (0.00635)
B. DID, county FEs	237.8*** (37.25)	−0.000299 (0.00280)	0.0230*** (0.00352)	0.0161*** (0.00226)	−0.0893*** (0.0118)	−0.0227*** (0.00874)	0.0363*** (0.00497)
C. CEM+ DID	190.5*** (43.9)	−0.01841*** (0.00435)	0.00793 (0.00618)	0.00945** (0.00368)	−0.00019 (0.01760)	−0.03160** (0.01319)	0.02800*** (0.00791)

Robust standard errors clustered by hospital in parentheses except for (B). Total volume in millions of points. A. Controlled for hospital fixed effects, accreditation level, ownership, and teaching status of hospitals and region.

B. Controlled for county fixed effects, accreditation level, ownership, and teaching status of hospitals and region; robust standard errors clustered by county in parentheses.

C. Hospitals matched using CEM (Iacus et al., 2011) on accreditation level, ownership, and teaching status of hospitals and region.

Significance levels:

^*p<0.10;

^**p<0.05;

^***p<0.01.