The shares closed at $15.16 - a full $1.53 down on their value at close of play on Tuesday.
In the past 52 weeks they have traded as high as $19.34, and as low as $12.
There was no obvious reason for the sharp decline in value, although one report suggested that the drop owed something to United's reported interest in defender Ezequiel Garay.
Rumours, even unfounded ones, can have an impact on listed companies' share prices. Social media can also work for and against companies, with rumours often spreading quickly on sites such as Twitter.
Garay, 26, currently plays for Benfica and is linked with a £17 million switch to Old Trafford this summer as David Moyes refreshes the side in his first season in charge.
Financial website Benzigna claimed that "the large cash disbursement for the defender does affect Manchester United's finances, who only reported cash of $113m as of the last filing."
Decisions taken on and off the field can have profound effects on clubs listed on stock exchanges.
United, who are owned by the Glazer family, but have listed an approximate 10% stake of the club on the NYSE, experienced a fall in value on the news of Sir Alex Ferguson's retirement last month.
When stocks began trading the day after Ferguson's announcement, there was an instant 4.5% fall in the share price, although it rallied considerably later on the same day.
"This stock probably has a lot of speculation built into it," said analyst Ken Perkins at the time in an interview with the BBC.
"It may not trade a lot on fundamentals, but may trade on things like who's the new manager, how the team performs.
"It's hard to say how other investors will feel. That's why in our view stock like Manchester United is risky."
With football a relatively recent entry to Stock Exchanges - Tottenham were the first English side to do so in the 1980s - it remains to be seen whether the impact of Twitter, fans' relatively recent obsession with transfer rumours, and the power of agents will have long-term impacts on the stability of clubs finances.