Estimated Autism Risk and Older Reproductive Age

The prevalence of autism, a developmental disorder characterized by serious impairments in social interaction and language development as well as stereotyped and repetitive behaviors, has increased dramatically over the past 2 decades from approximately 4 to 40 cases per 10 000. The cause of the increase is unknown, as is the etiology of autism. Evidence from twin studies suggests that autism is likely a genetic disorder. However, genetic causes for the vast majority of autism cases have not yet been identified through molecular genetic research. In addition, dozens of previous studies have identified a wide range of perinatal and parental risk factors. Despite these studies, our understanding of even the most basic of these factors, parental age, is muddled

Measurement Error in Panel Data: A Comparison of Face-to-Face and Internet Survey Samples

for suggestions and constructive criticism. She thanks Michael Rosenfeld for generously agreeing to share a restricted version of the HCMST data set

PVAR Estimates.

<p><i>Source</i>: CouchSurfing US dataset. Legend: *, ** , ***. N = 67,183.</p><p>Each variable is time-demeaned to take into account any secular trends. We controlled for heteroskedasticity by dividing each variable by its time dependent standard deviation. We addressed autocorrelation of individual observations by subtracting the forward mean, which corresponds to the mean of all future observations for each individual (Helmert transformation). The reported coefficients are -scores.</p

Graphical representation of the PVAR model with a three-lag period.

<p>L = number of logins (logs); D = number of ties; P = proportion of associational ties. Arrows represent statistically significant effects (at the 95% confidence level or more). Magnitude of the effects reported in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0067388#pone-0067388-t001" target="_blank">Table 1</a>.</p

Total logins by number of associational ties.

<p>Total logins by number of associational ties.</p

Ratio of ties by size of local chapters (top panel) and by (log) number of members (bottom panel).

<p>Each dot represents the total proportion of the two types of ties in a metropolitan area of the United States (CSA) as of December 2010 (N = 83.). We excluded CSAs where more than 90% of the members had no ties. In the top panel diamonds show the group means with 95% confidence intervals (One Way ANOVA, F ratio = 21.22, ). The bottom panel shows a quadratic fit to the data with 95% confidence interval. .</p