Table 2.

Coefficients in the Regression Model that Used Inflation Adjusted Income as the Dependent Variable

	Coefficient	95% confidence intervals	P value
Physician work effort
Total annual visits	$8.95	$7.05 to $10.84	<.001
Total annual hours worked	$4.55	$0.78 to $9.87	.09
Provider characteristics
Years in medical practice (5-10 years is referent)
Less than 5 years	$28,810	$45,399 to $12,222	.001
10 to 14 years	$8,992	$1,573 to $19,557	.10
15 to 19 years	$20,899	$9,467 to $32,332	<.001
20 to 24 years	$29,757	$16,268 to $43,247	<.001
25 to 29 years	$7,368	$8,237 to $22,974	.4
30 to 34 years	$19,091	$415 to $38,597	.06
35 to 39 years	$35,156	$57,666 to $12,647	.002
40 years or more	$47,991	$89,989 to $5,993	.03
Ownership interest, and board certification
Physician is an employee	$18,780	$27,027 to $10,533	<.001
Physician is board certified	$25,070	$14,332 to $35,807	<.001
Practice characteristics
Census region of practice (Southern is referent)
Northeast census region	$4,056	$14,127 to $6,014	.4
North Central census region	$5,783	$4,471 to $16,036	.3
Western census region	$4,670	$15,157 to $5,818	.4
Practice setting (population greater than 500,000 is referent)
Less than 50,000 population	$18,318	$33,244 to $3,392	.02
Population between 50,000 and 500,000	$3,111	$12,114 to $5,891	.5
Service population
1% increase in patient population on Medicaid	$258.69	$547.51 to $30.13	.08
Proportion providing Medicare services	$10,176	$22,013 to $42,366	.5
Race/gender characteristics (white male is referent)
Black male	$7,193	$31,054 to $16,669	.6
White female	$36,609	$47,633 to $25,585	<.001
Black female	$56,452	$93,383 to $19,520	.003

Adjusted R² for the model =.19.