Table 1.

Distribution of demographic factors in KNHANES¹, 1998, 2005 and 2009

Demographic group	1998		2005		2009		P value for percent4
	No. of subjects	Percent	No. of subjects	Percent	No. of subjects	Percent
Sample size (n)
Number of Individuals	10,400	100	8,930	100	9,391	100
Mean of Age2	33.1±0.4		35.3±0.3		37.3±0.4		<0.001
Age groups (%)
2-6 y	875	7.9	631	5.8	663	4.9	0.0723
7-12 y	911	9.1	915	9.1	889	7.2
13-18 y	980	10	747	8.1	738	8.9
19-39 y	3,416	35.4	2,511	34.8	2,248	32.5
40-59 y	2,565	24.5	2,574	28	2,517	30.5
60 y+	1,520	11.6	1,441	13.2	2,209	15.1
Gender (%)
Male	4,984	48.7	4167	50.2	4,182	50.2	<0.01
Adults (≥19 y) education (%)
<High school diploma	3,236	36.7	2,338	30.7	3,091	35.3	<0.001
≥High school diploma	4,276	63.3	4,201	69.3	3,909	64.7
Income as percentage of poverty (%)3
Low (<120%)	3,671	32.7	1,878	19.9	2,526	23.5	0.1884
Middle (120-250%)	4,340	45.9	3,495	40.1	3,292	37
High (≥250%)	1,961	21.5	3,403	39.9	3,443	39.5
Region (%)
Large City	4,130	47.9	4,102	47.1	4,069	46.4	<0.05
Small City	2,658	32	3,089	35.2	3,320	37.2
Rural	3,612	20.1	1,739	17.7	2,002	16.4

¹Weighted to be nationally representative.

²Mean±Standard Error.

³Calculated values based on poverty threshold of each year.

⁴χ²- test comparing the percent of each demographic group between 1998 and 2009.