Table 2.

Incidence proportions in the study population by birth year

Birth cohort	ADHD cases	Births	Incidence proportion (%)	95 % CI
1990	242	66,623	0.36	0.31; 0.41
1991	327	66,791	0.49	0.44; 0.55
1992	371	69,669	0.53	0.48; 0.59
1993	451	68,898	0.66	0.59; 0.72
1994	557	70,999	0.79	0.72; 0.85
1995	662	70,522	0.94	0.87; 1.01
1996	730	67,595	1.08	1.00; 1.61
1997	819	67,134	1.22	1.14; 1.31
1998	1028	65,092	1.58	1.49; 1.68
1999	1366	64,341	2.12	2.01; 2.24
2000	1665	64,630	2.58	2.46; 2.70