In the past, “non-practicing entities” (NPEs), popularly known as “patent trolls,” have helped small inventors profit from their inventions. Is this true today or, given the unprecedented levels of NPE litigation, do NPEs reduce innovation incentives? Using a survey of defendants and a...

This paper estimates the total cost of patent litigation to alleged infringers. We use a large sample of stock market event studies around the date of lawsuit filings for US public firms from 1984-99. We find that the total costs of litigation are much greater than legal fees and costs are large...