A Measure of Competition Based on 10‐K Filings

ABSTRACT In this paper we develop a measure of competition based on management's disclosures in their 10‐K filing and find that firms’ rates of diminishing marginal returns on new and existing investment vary significantly with our measure. We show that these firm‐level disclosures are related to existing industry‐level measures of disclosure (e.g., Herfindahl index), but capture something distinctly new. In particular, we show that the measure has both across‐industry variation and within‐industry variation, and each is related to the firm's future rates of diminishing marginal returns. As such, our measure is a useful complement to existing measures of competition. We present a battery of specification tests designed to explore the boundaries of our measure and how it varies with the definition of industry and the presence of other measures of competition.