Why do there appear to be missing sequential datasets in the restricted data?

The NSDUH 2-year restricted data datasets are generally sequential – 2006-2007, 2008-2009, 2010-2011, 2012-2013, 2014-2015, and 2016-2017. NSDUH underwent a partial redesign in 2015.

There are several measures that “broke trends” that year, so estimates from 2015 and later are no longer comparable to their 2014 and earlier counterparts. Because of this, an extra dataset was created for the restricted data for 2015-2016, but there is no 2-year dataset for 2013-2014.

After the 2015 redesign, the datasets include 2015-2016, 2016-2017, 2017-2018, and 2018-2019. There was another trend break in 2020, and no restricted dataset was created for that year. The sequential nature of the datasets begins again with 2021-2022.