The United States Bureau of Labor Statistics estimates that there are about 350,000 customer service representative jobs in the United States. The estimated median annual salary is about $34,710. The Bureau estimates that there are more customer service representative jobs than child care or security guard jobs (and customer service representatives make more than those many other jobs that don’t require a college degree!). These estimates aren’t just focused on call center agent positions (they seem to include jobs for customer service agents that work in retail locations as well).
Further, these numbers don’t include any estimates of sales agents who work in contact centers. There are a large number of sales contact center agent jobs in the U.S. as well. Often, these sales agent jobs pay more than customer service agent jobs because sales call center agents often get paid a commission in addition to a base hourly wage.
You can read more about the Bureau’s research about these jobs here.