Appendix A6.

Results from the sensitivity analysis with clustering by county

	Instrumental Variables (IV) analysis
Outcome	Estimate (Robust Standard Error)
Utilization
Log(Frequency of chemotherapy drug claims)	−0.07(0.03)*
Log(Frequency of chemotherapy administration claims)	−0.06(0.02)**
Spending ($)
Log(Chemotherapy drug spending)	0.18(0.05)***
Log(Chemotherapy administration spending)	0.08(0.04)**
Treatment mix
Log(Chemotherapy drug spending per claim)	0.25(0.04)***
First-Stage Statistics
Estimate on instrument (Robust Standard Error)	0.71(0.01)***
F-Statistic	5,442.43
N	81,899

Notes: Oncologist fixed effects are included in all models. Covariates controlled for in all models are year dummies, patient demographic characteristics, chronic condition indicators, cancer type, metastasis indicator, and ZIP-level socio-economic variables; Spending measures are adjusted to 2013 dollars;

^*p < 0.10,

^**p < 0.05,

^***p < 0.01.