In normal times, real activity moves sluggishly so familiar monthly and quarterly macroeconomic data provide information on a time scale that is sufficiently granular for macroeconomic monitoring and forecasting. But when macroeconomic conditions instead evolve rapidly – on a time scale of weeks or even days, as was the case during the first half of 2020 – it is important to have a systematic measure of real economic activity available at higher frequencies to inform the policy and business communities.
Lewis, Daniel J., Karel Mertens, James H. Stock, and Mihir Trivedi. "Measuring Real Activity Using a Weekly Economic Index." Federal Reserve Bank of New York, April 2020.