Table 2.

Unadjusted and adjusted results of predictors of annual generic drug prescribing rates (n=770,095)

Factors	Mean Annual Generic Drug Prescribing Rate Rate Ratio (99% Confidence Interval)1
	Unadjusted Models2	Adjusted Model3
Industry payments category
No payment	ref	ref
$100 and less	0.96 (0.96, 0.96)**	0.98 (0.97, 0.98)**
$100-500	0.93 (0.92, 0.93)**	0.95 (0.95, 0.95)**
More than $500	0.92 (0.92, 0.92)**	0.95 (0.95, 0.95)**
Prescriber characteristics
Sex
Male	ref	ref
Female	0.99 (0.99, 0.99)**	0.97 (0.97, 0.97)**
Region
Northeast	ref	ref
Midwest	1.05 (1.04, 1.05)**	1.05 (1.04, 1.05)**
South	1.03 (1.03, 1.03)**	1.03 (1.03, 1.03)**
West	1.03 (1.02, 1.03)**	1.02 (1.02, 1.02)**
Non-US	1.06 (1.05, 1.07)**	1.06 (1.05, 1.07)**
Prescriber practice factors
Specialty
Primary care	ref	ref
Medical specialty	0.91 (0.91, 0.91)**	0.92 (0.91, 0.92)**
Surgical specialty	0.93 (0.92, 0.93)**	0.93 (0.92, 0.93)**
Obstetrics/gynecology	0.81 (0.80, 0.81)**	0.82 (0.81, 0.82)**
Hospital-based specialty	1.09 (1.09, 1.09)**	1.07 (1.07, 1.08)**
Psychiatry	1.05 (1.05, 1.05)**	1.06 (1.06, 1.06)**
Non-physician, unknown	1.02 (1.01, 1.02)**	1.01 (1.01, 1.01)**
Annual number of distinct Medicare Part D beneficiaries served
0-50	ref	ref
51-100	1.00 (1.00, 1.00)*	1.01 (1.01, 1.01)**
101-250	1.01 (1.01, 1.02)**	1.02 (1.02, 1.03)**
251 and above	0.98 (0.98, 0.98)**	1.00 (1.00, 1.01)**

¹Generalized linear regression models with Poisson distribution

²Each factor as the only exposure variable without controlling for any other factors

³Industry payments as exposure variable, controlling for all covariates

^*P<0.01

^**P<0.001