Potential output is an estimate of what the economy could produce. Actual output is what the economy does produce. If actual is below potential a negative output gap there is “slack” in the economy. If actual is above potential—a positive output gap—resources are fully employed, or perhaps overutilized. The May 2021 issue of Page One Economics® explains how the output gap is useful for checking the health of the economy. It also points out how errors in the estimation of potential real GDP can reduce the effectiveness of policy.