Table 2.

ASD prevalence slopes: ADDM and IDEA snapshot versus tracking

State	Trend slope ± slope error (per 10,000 per year)a			IDEA slope ratioe bsnap/btrack	Recent 8 year-old prevalence (%)
	ADDMb,c b track	IDEAd b snap	IDEAd b track		ADDM (BY 2002 or 2004)f	IDEA (BY 2003)
Alabama		4.0 ± 0.9	5.4 ± 0.2	0.74	0.57	0.66
Arizona	9.1 ± 1.5	5.9 ± 0.3	8.0 ± 0.3	0.74	1.52	0.96
Arkansas		4.1 ± 0.6	5.8 ± 0.8	0.71	1.20	0.84
California	N/A	7.6 ± 0.2	9.7 ± 0.4	0.78	N/A	1.25
Colorado		3.4 ± 0.3	5.2 ± 0.4	0.67	1.08	0.61
Florida		6.6 ± 0.5	7.6 ± 0.7	0.87	N/A	0.98
Georgia	8.2 ± 0.8	3.4 ± 0.8	4.8 ± 0.4	0.70	1.55	0.80
Maryland	7.4 ± 2.0	5.0 ± 0.9	8.2 ± 0.5	0.61	1.16	1.15
Missouri		5.0 ± 0.6	7.5 ± 0.4	0.67	1.15	1.03
New Jersey	13 ± 0.9	9.8 ± 0.6	10.4 ± 0.6	0.94	2.46	1.46
No. Carolina	12 ± 1.3	5.0 ± 0.4	7.5 ± 0.4	0.67	1.69	1.04
Pennsylvania		9.6 ± 0.5	12.6 ± 0.5	0.76	N/A	1.53
S. Carolina	6.1 ± 1.4	4.0 ± 0.3	5.1 ± 0.5	0.78	1.24	0.74
Utah		2.0 ± 0.3	5.6 ± 0.4	0.36	1.73	0.76
W. Virginia		4.3 ± 0.7	5.2 ± 0.4	0.82	N/A	0.76
Wisconsin	4.7 ± 0.9	6.0 ± 0.5	8.1 ± 0.3	0.74	1.08	1.22

^aTo convert to %/year, divide by 100

^bThe ADDM 8 year-old tracking slope is reported only when the least squares linear regression slope b_track is statistically different from 0 at a confidence level of p < 0.01 or better

^cFor ADDM data, the birth year span ranges from as early as 1992 to as late as 2004. See Fig. 5 and Supplementary File S4 for individual state details

^dFor all IDEA data, the birth year span is 1994–2003, the tracking age is 8 years old and the 2011 IDEA snapshot age range is 8–17 years old

^e b_snap/b_track slope ratios are shown in bold face, indicating smaller uncertainty, when the slope error is ≤ 10% of the regression slope for both b_track and b_snap

^fBirth Year (BY) 2004 prevalence shown if available, otherwise BY 2002