. Author manuscript; available in PMC: 2020 Apr 1.

Published in final edited form as: Health Econ. 2019 Jan 29;28(4):517–528. doi: 10.1002/hec.3860

Appendix A5.

Comparison of results between using original and log-transformed outcomes

	Estimate (Robust Error)
	Difference-in-differences (DD) Analysis		Instrumental Variables (IV) analysis
Outcome	Original outcomes	Log outcomes	Original outcomes	Log outcomes
Quantity
Frequency of chemotherapy drug claims	−0.33(0.18)^*	−0.04(0.02)^**	−0.65(0.29)^**	−0.07(0.03)^***
Frequency chemotherapy administration claims	−0.47(0.26)^*	−0.03(0.02)^*	−0.74(0.35)^**	−0.06(0.03)^**
Spending ($)
Chemotherapy drug spending	1,224.51(469.19)^**	0.15(0.05)^***	1,258.08(777.49)	0.18(0.05)^***
Chemotherapy administration spending	235.91(47.69)^***	0.09(0.03)^***	227.30(59.59)^***	0.08(0.04)^*
Treatment mix
Chemotherapy drug spending per claim	295.90(78.73)^***	0.19(0.03)^***	387.30(136.67)^***	0.25(0.05)^***

Notes: Oncology 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; Standard errors account for clustering within practices; Spending measures are adjusted to 2013 dollars;

p < 0.10,

^**

p < 0.05,

^***

p < 0.01.