Table 5.

Distribution of selected variables in 698 participants of the GCS who were interviewed twice, ∼4 years apart^a

	Percentb
Characteristic	First interview	Second interview	Kappa statistics
Ethnicity			1.00
Turkmen	97.4	97.4
Non-Turkmen	2.6	2.6
Highest educational level			0.87c
University/college	1.3	1.6
9–12 years at school	3.9	2.7
6–8 years	3.0	2.3
1–5 years	12.9	12.2
No schooling	78.9	81.2
Tobacco smoking			0.85
Ever smoker	11.3	11.9
Never smoker	88.7	88.1
Nass chewing			0.78
Ever chewer	4.7	5.0
Never chewer	95.3	95.0
Opium consumption			0.76
Ever user	11.8	14.6
Never user	88.2	85.4

^aThe mean interval between the two interviews was 45 months.

^bAll data are column percentages.

^cWeighted kappa statistic.