Americans racked up approximately $7.2 trillion in purchases for goods and services last year, according to the Selig Center for Economic Growth at the University of Georgia. Marketers and their media partners are increasingly curious to know exactly when and where those dollars are being spent. For instance, the radio industry is intrigued by the relationship between key dayparts, like â€œdrive time,â€? and consumer spending. This month, we decided to examine just how Americans shop around the clock. Data from New York City-based research firm Simmons Market Research Bureau reveals that more than twice as many consumers are out shopping on Saturday and Sunday than at almost any time during the week. Not only are there more shoppers crowding stores on weekends, but the customers are also dropping more cash on their purchases. According to Indianapolis-based market research firm Stillerman Jones & Company, the average consumer spends $78 per trip at the mall on weekends and only $67 per trip during the week. Of course, not everyone likes shopping with the masses. Americans who are unemployed tend to do the bulk of their grocery shopping during the week, unlike those who are employed. In addition, the Internet now allows us to shop 24/7. Research provided by Reston, Va.-based comScore Networks shows that an estimated 20 percent of online spending occurs between 9 p.m. and 9 a.m., when most stores are closed.