The reason for using census figures when setting a national threshold is that the only aim of these figures would be to identify the minimum number of communities to be designated.
Y rheswm am ddefnyddio ffigyrau cyfrifiad wrth osod trothwy cenedlaethol yw mai unig nod y ffigyrau hyn fyddai adnabod isafswm o gymunedau lle byddai dynodiad.