Table 1.

Distribution of explanatory variables within groups by caries experience

		Percentage
		Total	Within caries groups (DMFT = 1 or more)
			Yes	No
Sex	Females	49.9%	55.1%	44.0%
	Males	50.1%	44.9%	56.0%
Age	12 years	32.8%	31.1%	34.6%
	14 years	33.2%	32.6%	33.9%
	17 years	34.0%	36.4%	31.5%
Ethnicity	Han	50.9%	45.1%	57.2%
	Zhuang	34.2%	46.1%	21.2%
	Yao	14.9%	8.8%	21.6%
Area of residence	Rural	57.7%	56.1%	59.5%
	Urban	42.3%	43.9%	40.5%
Watch TV	<30 minutes/day	36.0%	34.1%	38.0%
	30-60 minutes/day	25.0%	24.9%	25.2%
	60-120 minutes/day	21.3%	21.5%	21.1%
	120-180 minutes/day	9.3%	10.5%	8.0%
	>180 minutes/day	8.4%	9.0%	7.7%
Eat breakfast	Everyday	85.6%	86.6%	84.7%
	Less often	14.3%	13.4%	15.3%
Milk consumption	Never	12.6%	11.7%	13.6%
	Sometimes	65.1%	66.4%	63.6%
	Once/day	17.0%	16.8%	17.1%
	More than once/day	5.3%	5.0%	5.7%