Analyzing and forecasting the performance and direction of a large, complex economy like that of the United States is a difficult task. The process involves parsing a great deal of data, understanding key economic relationships, and assessing which events or factors might cause monetary or fiscal policymakers to change policy. One purpose of this article is to reinforce several key principles that are useful for tracking the U.S. economy’s performance in real time. Two principles stand out: First, the economy is regularly hit by unexpected economic disturbances (shocks) that policymakers and forecasting models cannot predict. Second, most key data used to measure the economy and track its performance are often revised—and by substantial amounts.