Table 1.

Survey methods and demographic profiles of the 2011 survey and the 2014 survey

	2011 survey Reference [11]	2014 survey
Survey methods
No. of questionnaire items	18 questions	20 questions (2 questions were added)
Data collection method	Online	Online
Sample size	1000	1000
Demographics
Gender
Male	499	498
Female	501	502
Age (yr)
20–29	207	190
30–39	237	222
40–49	231	236
50–59	206	221
60–69	119	131
Region of residence
Seoul	541	538
Daejeon	79	77
Daegu	125	128
Busan	182	186
Gwangju	73	71