Table 1: Definitions of the dependent and independent variables.

Variable

Dependent variables
 ProbabilityTraffic accident with head injury = 1; other = 0
 Medical costNT dollarsa
 Length of stay in hospitalInpatient days

Independent variables
 Policy After motorcycle helmet use law = 1;
Before motorcycle helmet use law = 0

Geographic location
 NorthPatient lived in Taipei City, Keelung City, Taipei County, Yilan County, Hsinchu City, Taoyuan County, Hsinchu County, and Miaoli County; yes = 1, other =0
 CenterPatient lived in: Taichung City, Taichung County, Changhua County, and Nantou County; yes = 1, other = 0
 SouthPatient lived in: Tainan City, Chiayi City, Yunlin County, Chiayi County, Tainan County, Kaohsiung City, Kaohsiung County, Pingtung County, and Penghu County; yes = 1, other = 0
 EastPatient lived in: Hualien County and Taitung County; yes , other =0

GenderMale = 1; female = 0

Age
 ChildrenPatient’s age from 0 to 14 years old = 1; other = 0
 Adult 15–24Patient’s age from 15 to 24 years old = 1; other = 0
 Adult 25–64Patient’s age from 25 to 64 years old = 1; other = 0
 ElderlyPatient’s age over 65 years old = 1; other = 0

Rural/urban b
 Special municipalityPatient lived in special municipality (regions with populations of not less than 1,250,000 and have special requirements in their political, economic, cultural, and metropolitan developments) = 1; other = 0
 CityPatient lived in city (regions with populations of not less than 500,000 but not more than 1,250,000 and occupy major political, economic, and cultural roles) = 1; other = 0
 County administeredPatient lived in county-administered (regions with populations of not less than 150,000 but not more than 500,000, and possess thriving industrial and commercial development, adequate financial resources for self-government, convenient transportation, and comprehensive public facilities) = 1; other = 0
 TownPatient lived in town (regions with populations of less than 150,000, and possess thriving industrial and commercial development) = 1; other = 0
 VillagePatient lived in village (regions with populations of less than 150,000, and less economic development) = 1; other = 0

aUS$1 = NT$33.4 in 1998.
bRural/urban stratify according to the Local Government Act.