Table 1. General characteristics of the study participants at baseline.

	Total		2002		2003
	n	%	n	%	n	%
Total	18,029		9109		8920
Income
Quartile 1 (low)	1117	6.2	572	6.3	545	6.1
Quartile 2 (mid-low)	5171	28.7	2693	29.6	2478	27.8
Quartile 3 (mid-high)	8576	47.6	4288	47.1	4288	48.1
Quartile 4 (high)	3165	17.6	1556	17.1	1609	18.0
Income trajectory
Consistently low	1026	5.7	466	5.1	560	6.3
Consistently mid-low	3039	16.9	1615	17.7	1424	16.0
Mid-low to mid-high	1632	9.1	854	9.4	778	8.7
Consistently mid-high	7527	41.7	3761	41.3	3766	42.2
Decreasing	911	5.1	470	5.2	441	4.9
Mid-high to high	640	3.5	328	3.6	312	3.5
Consistently high	3254	18.0	1615	17.7	1639	18.4
Sex
Men	9388	52.1	4755	52.2	4633	51.9
Women	8641	47.9	4354	47.8	4287	48.1
Location
Rural	5490	30.5	2809	30.8	2681	30.1
Urban	12,539	69.5	6300	69.2	6239	69.9
Low birth weight (<2500 g)
No	17,894	99.3	9050	99.4	8844	99.1
Yes	135	0.7	59	0.6	76	0.9
Conduct disorders (aggressive disorder, oppositional defiant disorder)
No	18,009	99.9	9098	99.9	8911	99.9
Yes	20	0.1	11	0.1	9	0.1
Emotional disorders (depression, anxiety)
No	17,808	98.8	8996	98.8	8812	98.8
Yes	221	1.2	113	1.2	108	1.2
Social disorders
No	18,000	99.8	9091	99.8	8909	99.9
Yes	29	0.2	18	0.2	11	0.1
Tic disorders
No	17,830	98.9	9004	98.8	8826	98.9
Yes	199	1.1	105	1.2	94	1.1
Autism spectrum disorders
No	18,000	99.8	9091	99.8	8909	99.9
Yes	29	0.2	18	0.2	11	0.1
Developmental disorders
No	17,763	98.5	8945	98.2	8818	98.9
Yes	266	1.5	164	1.8	102	1.1
Intellectual disability
No	17,950	99.6	9061	99.5	8889	99.7
Yes	79	0.4	48	0.5	31	0.3