A note on industry concentration measurement

Industry concentration—the share of sales or output accounted for by the largest firms within an industry—has received widespread attention recently, in part because concentration has generally risen in recent decades (figure 1). Measurement challenges are at the core of concentration-based inquiry: industry sales concentration is one of the lowest-frequency business statistics produced by the U.S. statistical agencies, with concentration data being released only twice per decade as part of the Economic Censuses.