The pooled analysis combined four years of National Survey data (2016 to 17 to 2019 to 20) on four National Indicators.
Fe wnaeth y dadansoddiad cyfunol gyfuno pedair blynedd o ddata’r Arolwg Cenedlaethol (2016 i 2017 i 2019 i 2020) ar bedwar Dangosydd Cenedlaethol.