The corresponding figure in April to June 2018 was 22% and has fallen in each April to June since then, but with seasonal variations in the percentage during other quarters of the year.
Y ffigwr cyfatebol rhwng Ebrill a Mehefin 2018 oedd 22% ac mae wedi gostwng ym mhob Ebrill i Fehefin ers hynny, ond gydag amrywiadau tymhorol yn y ganran yn ystod chwarteri eraill y flwyddyn.