Table 1.

Characteristics of subjects who were mailed questionnaires and of enrolled subjects.

	Mailed	Responded
Age group	Total	Total	Males	Females	Unknown	Response rate
Under 1 year	11	5	4	1	0	45%
1 year	16	9	5	4	0	56%
2 years	9	3	3	0	0	33%
Preschool	60	24	12	12	0	40%
Elementary school	102	39	20	19	0	38%
Junior-high school	75	37	14	21	2	49%
High school	70	26	13	13	0	37%
Unknown but <18 years		1	0	1	0
18 to 29 years	363	110	55	55	0	30%
30 to 49 years	537	229	90	137	2	43%
50 to 64 years	693	304	139	162	3	44%
65 to 79 years	532	275	135	138	2	52%
80 years or older	197	100	39	58	3	51%
Unknown but ≥18 years		20	5	4	11
Total	2665	1182	534	625	23	44%