On 22 July 2015, United had a market capitalisation of £2.23bn. On Monday night it was down £650m to £1.58bn.
United's poor performance in this season's Champions League and problems qualifying for the next season's competition are having a significant impact on the share price.
Dropping out of the Champions League after losing to Wolfsburg in December caused the share price to fall by five per cent to $17.82 (£12.45). It has continued to fall as United have struggled to secure a top-four finish in the Premier League.