Does Option Trading Have a Pervasive Impact on Underlying Stock Prices

The question of whether and to what extent option trading impacts underlying stock prices has been a focus of intense interest since options began exchange-based trading in 1973. Despite considerable effort, no convincing evidence for a pervasive impact has been produced. A recent strand of theoretical literature predicts that rebalancing by traders who hedge their option positions increases (decreases) underlying stock return volatility when these traders have net written (purchased) option positions. This paper tests this prediction and finds a statistically and economically significant negative relationship between stock return volatility and net purchased option positions of investors who are likely to hedge. Hence, we provide the first evidence for a substantial and pervasive influence of option trading on stock prices.