In less than a year’s time, the federal government is again revising the prevalence of autism upward, saying the developmental disorder now affects 1 in 50 children.

The latest estimate released Wednesday by the U.S. Centers for Disease Control and Prevention comes from a national telephone survey of nearly 100,000 parents conducted in 2011 and 2012.

Parents were asked a number of health questions about their kids including whether they had ever been told by a doctor that their child had an autism spectrum disorder. The results suggest that autism is occurring in 2 percent of school-age children.

That’s substantially higher than prevalence numbers the CDC released just last March which put the rate of autism at 1 in 88 American children. That previous estimate relied on a study of health and education records collected on 8-year-olds. The current research included kids ages 6 to 17, but is considered by some to be less reliable since it is based on parent-reported information.

Federal officials say the increase is largely due to better diagnosis of autism spectrum disorders. The jump in prevalence was most pronounced among older kids with milder forms of the condition.

Consistent with previous findings, the survey found that boys were four times more likely than girls to have autism.