Table 6.

IV Estimates of Proximity Effect on Drug Utilization

	Outcome: New Drug Use
	(1)	(2)	(3)
A. Reduced form: Drug receipt effect
Residence in first author HRR	0.0228** (0.0099)	0.0217** (0.0099)	0.0228** (0.0099)
Residence in other author HRR	0.0038 (0.0044)	0.0044 (0.0050)	0.0046 (0.0061)
Residence in first author’s neighbor HRR			0.0035 (0.0045)
Residence in other author’s neighbor HRR			− 0.0028 (0.0028)
B. Two-stage least squares
Provider in first author HRR	0.0293** (0.0127)	0.0259** (0.0114)	0.0263** (0.0115)
Provider in other author HRR	0.0056 (0.0058)	0.0060 (0.0061)	0.0065 (0.0061)
Sample
Author HRR only?	No	Yes	No
Number of observations	659,468	286,637	659,468

Reduced-form results report coefficients from three regressions where the outcome variable is new drug use and the key explanatory variables are indicators for whether a given patient resides in the same region as the study author (or in column 3, in a neighboring region). In panel B, the two-stage least squares results use patient residence variables as instrumental variables for whether the patient is treated in the author region. All regressions include drug-year fixed effects and HRR-cancer type fixed effects defined using three categories of cancer drugs: urologic, hematologic, and other (including breast, colon, lung, and brain). Standard errors clustered at the HRR-drug level shown in parentheses.

^*p < 0.10,

^**p < 0.05, and

^***p < 0.01.