In economics, the term sunspots (or sometimes 'a sunspot') usually refers to an 'extrinsic' random variable, that is, a random variable that does not directly affect economic fundamentals (such as endowments, preferences, or technology). 'Sunspots' can also refer to the related concept of extrinsic uncertainty, that is, economic uncertainty that does not come from variation in economic fundamentals. David Cass and Karl Shell also coined the term "sunspots" as a suggestive and less technical way of saying "extrinsic random variable".
The name is a whimsical reference to 19th-century economist William Stanley Jevons, who attempted to correlate business cycle patterns with sunspot counts (on the actual sun) on the grounds that they might cause variations in weather and thus agricultural output.[8] Subsequent studies have found no evidence for the hypothesis that the sun influences the business cycle.