A pet food company with an eCommerce store is currently working with two different media agencies to drive online sales through Paid Search advertisements. They user a parameter in the Tracking Code…

A pet food company with an eCommerce store is currently working with two different media agencies to drive online sales through Paid Search advertisements. They user a parameter in the Tracking Code variable to distinguish between traffic driven by each agency, and they would like to understand which agency is more effective at driving sales. Which metric should they use to compare and evaluate the agencies Return on Investment (ROI) performance?