GMAT Test Prep: CR-59765005 GMAT Critical Reasoning

In 1999, America Mart, which previously only sold through retail outlets, began selling on the internet while keeping its retail stores open. Total sales increased in 1999, but profits were less than in 1998.

Which of the following, if true, contributes most to explaining why America Mart's profits were more in 1998 than in 1999?