At least 8 million viewers tune in Sunday to season four premiere . That 's up from 6 million at the start of ` ` ' 's '' season three . PBS also says the show has become a post - holiday tradition .
At least 10.2 million viewers tune in Sunday to season 4 premiere . That 's up from 7.9 million at the start of `` Downton 's '' season three . PBS executive says the show has become a post-holiday tradition .