New federal figures indicate that autism prevalence among young children is on the rise.

The number of 4-year-olds with the developmental disorder increased from 1 in 75 children in 2010 to 1 in 59 kids in 2014, according to data published in the Center for Disease Control and Prevention’s Morbidity and Mortality Weekly Report.

The report out this month is among the first to detail the CDC’s findings on 4-year-olds. It is based on information collected by researchers at sites in Arizona, Colorado, Missouri, New Jersey, North Carolina, Utah and Wisconsin in 2010, 2012 and 2014. Some sites collected data in all three years, but others only participated part of the time.

Like in previous reports, autism was more common among boys than girls. Kids diagnosed at age 4 were significantly more likely than 8-year-olds to have co-occurring intellectual disability, the study found, suggesting that those with more severe symptoms are flagged sooner.

Children with autism in some states were far more likely than others to receive their first evaluation by age 3. And, in what experts called a concerning finding, there was no improvement over time in the age of first evaluation at the three sites which collected data across 2010, 2012 and 2014.