For a given industry, the capacity utilization rate is equal to an output index divided by a capacity index. The Federal Reserve Board's capacity indexes attempt to capture the concept of sustainable maximum output-the greatest level of output a plant can maintain within the framework of a realistic work schedule, after factoring in normal downtime and assuming sufficient availability of inputs to operate the capital in place.
NAICS = 21
Source Code: CAPUTL.G21.S
Board of Governors of the Federal Reserve System (US), Capacity Utilization: Mining [CAPUTLG21SQ], retrieved from FRED, Federal Reserve Bank of St. Louis; https://fred.stlouisfed.org/series/CAPUTLG21SQ, October 18, 2018.