In the United States, a large fraction of transactions among banks takes place over Fed-wire, which is an electronic payments system operated by the Federal Reserve System. In December 2015, the volume of funds transfers on Fedwire was about $72 trillion, which was more than four times annual GDP in 2015. Do these statistics indicate that there might be some large measurement error in the official U.S. national in-come accounts, or is this entirely consistent with official GDP numbers being accurate measures of aggregate economic activity? Explain, and discuss your answer.