The decline put the stock at a one-year low and left it down by more than 20% so far in 2018.
Rather than reacting to any specific news from the company, investors appeared to push Groupon's stock lower as part of a broader general pessimism around its business. Shares fell through the first half of 2018 as the company struggled with net losses while working to build a more defensible position in the local advertising industry.
Groupon's most recent earnings report showed minor progress in a few of management's goals, including improved profitability in international markets and a large, albeit steady, active customer base in the U.S. Still, Groupon has lost money in three of the last five fiscal years and current trends suggest 2018 will mark another year of red ink for the tech-based deals specialist.