The Sun (United Kingdom):

The Daily Star had been launched in 1978 by Express Newspaper, and by 1981 had begun to affect sales of The Sun. Bingo was introduced as a marketing tool and a 2p drop in cover price removed the Daily Star's competitive advantage opening a new circulation battle which resulted in The Sun neutralising the threat of the new paper. The new editor of The Sun, Kelvin MacKenzie, took up his post in 1981 just after these developments, and "changed the British tabloid concept more profoundly than [Larry] Lamb did", according to Bruce Page, MacKenzie The paper became "more outrageous, opinionated and irreverent than anything ever produced in Britain".

Please answer a question about this article. If the question is unanswerable, say "unanswerable". By what year had The Daily Star started impacting The Sun's sales?
1981