In May 2020, the two main financial regulators in the United States (the SEC and CFTC) launched investigations into the multi-billion-dollar US Oil Fund (USO). Over the last decade, USO has attracted huge numbers of private household investors eager to invest in oil. Its shares are easily bought and sold on internet trading platforms and the share price closely tracks movements in the spot price of the West Texas Intermediate (WTI) crude oil benchmark. But USO has been a volatile investment proposition.