Table 3.

Examination of the Exclusion Restriction Assumption for the Instrumental Variable (2008 Data)

Characteristics	Physicians' PIM Rates <Median		Physicians' PIM Rates ≥Median
Total	40,525		35,745
Female (N, %)	21,564	53.21	19,435	54.37
Age (mean, SD)
<70	13,102	32.33	11,946	33.42
70–79	19,767	48.78	17,364	48.58
80+	7,656	18.89	6,435	18.00
NHI enrollment category (N, %)
<NTD 40,000	4,961	12.24	4,251	11.89
NTD 40,000+	5,741	14.17	4,417	12.36
Farmers and fishermen/members of occupational unions	16,959	41.85	17,917	50.12
Low‐income household	299	0.74	319	0.89
Others	12,565	31.01	8,841	24.73
Hospitalization in the previous year (N, %)	6,941	17.13	5,961	16.68
Charlson comorbidity index (N, %)
Score 0	18,084	44.62	18,174	50.84
Score 1	11,952	29.49	10,423	29.16
Score 2+	10,489	25.88	7,148	20.00
Average number of medications per prescription (mean, SD)	3.23	1.25	3.41	1.24
UPC index by physician (N, %)
Low	14,034	34.63	11,147	31.18
Intermediate	13,226	32.64	11,657	32.61
High	13,265	32.73	12,941	36.20
Level of most frequently visited institution (N, %)
Medical center hospital	9,292	22.93	4,016	11.24
Regional hospital	9,195	22.69	6,549	18.32
District hospital	5,876	14.50	5,203	14.56
Community clinics	16,162	39.88	19,977	55.89
Area of most frequently visited institution (N, %)
Taipei area	14,340	35.39	8,998	25.17
Northern area	5,559	13.72	5,030	14.07
Central area	7,180	17.72	7,011	19.61
Southern	6,102	15.06	7,004	19.59
Kao‐ping area	6,388	15.76	6,468	18.09
Eastern area	956	2.36	1,234	3.45

NHI, national health insurance; PIM, potentially inappropriate medication; SD, standard deviation; UPC index, usual provider care index.