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At least 164 papers have defined a ‘patent thicket’ since the first mention of the term in 1988. There is no canonical definition. Instead authors use the term to refer to various combinations of seven different underlying economic issues. An average paper in 2001 used a definition based on 1.2 of these issues, and the complexity of definitions grew by 35% over the following decade. This increase in definitional complexity is partly a response to a growing sophistication in the broader literature on the economics of patents. However, repeat authors are frequently inconsistent in their definitions, and overall there is evidence of a growing confusion concerning patent thickets. Our analysis largely resolves this confusion. It also suggests that ill-advised policy reform efforts, and not patent thickets themselves, threaten the health of the innovation economy.