Is physician location sensitive to changes in patients’ financial responsibility?

Figures & data

Table 1. Data summary for physicians

		Pre-Period (2009–2011)	Post-Period (2012–2013)
Pa:	Share Male	0.45	0.46
Pa:	Mean Age	52.77	52.97
Pa:	Share w/Charlson Index = 0	0.93	0.93
Ph:	Share Time at ASC	0.71	0.78
Ph:	Share Time at ASC (w/CalPERS patient)	0.72	0.85
Ph:	Share Time at ASC (w/control group patient)	0.71	0.77
Ph:	Share CalPERS patients	0.11	0.10
Ph:	Avg Physician fee ($)	517.23	511.17
Ph:	Avg Physician fee – ASC ($)	518.43	492.05
Ph:	Avg Physician fee – Hospital ($)	514.32	578.62
N		35,370	25,120

Note: The sample consists of colonoscopy patients who visit Splitter physicians (i.e., physicians who work at both hospitals and Ambulatory Surgery Centers in 2011). Data is limited to patient observations for those who visit physicians observed in all years of 2011, 2012 and 2013 and excludes physician groups. Data for 2009 and 2010 is included if it is available. Pa = Patient Characteristics; Ph = Physician Characteristics. “Avg Physician fee” refers to the average reimbursement that physicians receive per-procedure performed.

Table 2. Patient data summary statistics

		Pre-Period (2009 − 2011)	Post-Period (2012 − 2013)
Pa:	Share Male	0.45	0.46
Pa:	Mean Age	52.77	52.97
Pa:	Share w/Charlson Index = 0	0.93	0.93
Ph:	Share Time at ASC	0.71	0.78
Ph:	Share Time at ASC (w/CalPERS patient)	0.72	0.85
Ph:	Share Time at ASC (w/control group patient)	0.71	0.77
Ph:	Share CalPERS patients	0.11	0.10
Ph:	Avg Physician fee ($)	517.23	511.17
Ph:	Avg Physician fee – ASC ($)	518.43	492.05
Ph:	Avg Physician fee – Hospital ($)	514.32	578.62
N		35,370	25,120

Note: The sample consists of colonoscopy patients who visit Splitter physicians (i.e., physicians who work at both hospitals and Ambulatory Surgery Centers in 2011). Data is limited to patient observations for those who visit physicians observed in all years of 2011, 2012 and 2013 and excludes physician groups.

Figure 1. Share of patients treated at an ambulatory surgery center (ASC).

This figure presents coefficients estimates of ρ from the event study in Equation 2. Each estimate represents the added effect of CalPERS membership on the probability of a patient being treated at an ASC, conditional on receiving a colonoscopy from a Splitter physician (i.e., physicians who work at both hospitals and Ambulatory Surgery Centers in 2011).

Table 3. OLS difference-in-difference regression results where outcome is 1(ASC)

Variable	(1)
Post	0.071*** (0.014)
Treat	−0.011 (0.009)
PostxTreat	0.064*** (0.018)
1(Charlson = 1)	−0.054*** (0.008)
1(Charlson = 2	−0.058***(0.011)
1(Age 30–39 Yrs)	0.002 (0.015)
1(Age 40–49 Yrs)	0.010 (0.012)
1(50–59 Yrs)	0.010 (0.012)
1(60–64 Yrs)	0.001 (0.014)
1(Male)	0.007* (0.004)

Note: This table reports OLS coefficients from regressions where the outcome is 1(ASC). The sample consists of colonoscopy patients who visit Splitter physicians (i.e., physicians who work at both hospitals and Ambulatory Surgery Centers in 2011). Also note that: 1: ***p ≤ 0.01, **p ≤ 0.05, *p ≤ 0.10. 2: Standards errors are clustered at the physician-level- there are 213 clusters. Physician fixed effects are included.

Figure 2. Work day variation among physicians.

Figure 2a presents the average number of days worked in an ASC for physicians in the quarters since reference pricing. Figure 2b presents the average share of days worked at an ASC in a given quarter. Figure 2c presents the average number of days worked in an ASC in the quarters since reference pricing. Figure 2d presents estimates of the added share of working days spent at an ASC in a given quarter, in comparison to the quarter before the reform is introduced, which has been benchmarked to zero. Data is from colonoscopy patient who visits to Splitter physicians (i.e., physicians who work at both hospitals and Ambulatory Surgery Centers in 2011).

Table 4. OLS regression results where outcome is 1(ASC)

	Owners	Non-Owners	Owners & Non-Owners
	(1)	(2)	(3)
Post	0.095*** (0.019)	0.030 (0.019)	0.030 (0.019)
Treat	−0.018* (0.010)	0.000 (0.013)	0.001 (0.013)
Post × Treat	0.066*** (0.022)	0.063** (0.029)	0.062** (0.029)
1(Owner) × Post			0.065** (0.027)
1(Owner) × Treat			−0.020 (0.016)
1(Owner) × Post × Treat			0.004 (0.037)
1(Charlson = 1)	−0.056*** (0.009)	−0.050*** (0.015)	−0.054*** (0.008)
1(Charlson = 2)	-0.069*** (0.014)	-0.038** (0.015)	-0.058*** (0.011)
1(Age 30–39 Yrs)	0.019 (0.019)	−0.026 (0.026)	0.002 (0.015)
1(Age 40–49 Yrs)	0.027 (0.018)	−0.016 (0.018)	0.011 (0.013)
1(Age 50–59 Yrs)	0.025 (0.017)	−0.014 (0.018)	0.011 (0.012)
1(Age 60–64 Yrs)	0.013 (0.019)	−0.018 (0.019)	0.002 (0.014)
1(Male)	0.008* (0.004)	0.006 (0.007)	0.007* (0.004)
N	37,023	23,467	60,490

Note: The sample consists of colonoscopy patients who visit Splitter physicians (i.e., physicians who work at both hospitals and Ambulatory Surgery Centers in 2011) that can be identified as owners or non-owners in the data. The table reports coefficient estimates where the outcome is 1(ASC). Also note that: 1: ***p 0.01, **p 0.05, *p 0.10 2: Standards errors are clustered at the physician-level; 120 clusters for owners; 93 clusters for non-owners; 213 clusters for owners and non-owners. 3: Physician fixed effects are included in all specifications.

Table A1. Robustness check – OLS difference-in-difference regression results where outcome is 1(ASC) and physician type is defined using two years of data

Variable	(1)
Post	0.061*** (0.015)
Treat	−0.010 (0.009)
PostXTreat	0.058*** (0.018)
1(Charlson=1)	−0.049*** (0.009)
1(Charlson=2)	−0.055*** (0.011)
1(Age 30–39Yrs)	−0.002 (0.014)
1(Age 40–49Yrs)	0.006 (0.012)
1(50–59Yrs)	0.008 (0.012)
1(60–64Yrs)	−0.002 (0.013)
1(Male)	0.007* (0.004)
N	61,388

Note: This table reports coefficient estimates where the outcome is 1(ASC). The sample consists of colonoscopy patients who visit Splitter physicians (i.e., physicians who work at both hospitals and Ambulatory Surgery Centers in 2010 and 2011). Also note that: 1: ***p0.01, **p0.05, *p0.10.

: Standards errors are clustered at the physician-level – there are 215 clusters.3: Physician fixed effects are also included.

Table A2. Robustness check – OLS Difference-in-difference regression results where outcome is 1(ASC) and physician groups are included

Variable	(1)
Post	0.067*** (0.014)
Treat	0.007 (0.009)
PostxTreat	0.075*** (0.018)
1(Charlson=1)	−0.062*** (0.007)
1(Charlson=2)	−0.063*** (0.008)
1(Age 30–39Yrs)	0.019 (0.015)
1(Age 40–49Yrs)	0.026* (0.015)
1(50–59Yrs)	0.025* (0.015) (0.014)
1(Male)	0.006* (0.003)
N	113,106
N	60,490

Note: This table reports OLS coefficients from regressions where the outcome is 1(ASC). The sample consists of colonoscopy patients who visit Splitter physicians (i.e., physicians who work at both hospitals and Ambulatory Surgery Centers in 2011). Also note that: 1: ***p≤0.01, **p≤0.05, *p≤0.10. 2: Standards errors are clustered at the physician-level – there are 283 clusters. 3: Physician fixed effects are also included.