Groupon ( GRPN ) shares dropped Tuesday after analysts at Goldman Sachs slapped a sell rating on the stock of the coupon company and cut its price target. At last check the stock was off nearly 9% to $2.40 after Goldman cut its rating from neutral, citing weakness across several key metrics of Groupon's business. Goldman in particular cited seven quarters of declines in the number of customers, weakness in the North American operations, and a dimmer forecast on revenue, billings and gross profit for 2020 and 2021. The firm slashed its price target for the Chicago company to $2.40 a share from $3.20. While Groupon has invested heavily to improve the customer experience with a mobile app, card-linked offers, online booking and an overall expansion in offers, Goldman analysts wrote they are concerned about the decline in customers, which appears to be accelerating. Groupon has lost 2.9 million customers through the first nine months of 2019, Goldman said. The drop is the "worst on record."