From the data you presented in the two tables, explain whether there is any evidence for a change in autism prevalence rates in children aged 8 years during the years 2004 to 2009.

Table 1
Year	Number of boys in the study population	Number of cases	Prevalence	Number of new cases in this year	Incidence
2004	145483	521	48%	172	12%
2005	143721	535	49%	170	12%
2006	147049	568	52%	190	13%
2007	142229	540	50%	173	12%
2008	138847	543	51%	170	12%
2009	138317	566	54%	180	13%

Table 2
Year	Number of girls in the study population	Number of cases	Prevalence	Number of new cases in this year	Incidence
2004	136752	109	10%	27	2%
2005	135511	112	10%	30	2%
2006	138548	112	11%	34	2%
2007	134083	125	12%	41	3%
2008	130876	107	10%	29	2%
2009	130367	106	10%	30	2%

From the data presented in the two tables, explain if there is evidence for a change in autism prevalence rates in children aged 8 during the years 2004 to 2009