i recent sold some calls that expired exactly at the money and ended up getting fully assigned on them, which I am told is unusual when there is no news or after hours move in the underlying stock. I wanted to know if this was just bad luck, or if many of those contracts were voluntarily exercised despite not being ITM. However, I had no luck getting my broker to disclose any details of the particular lottery used (i.e. the odds or % of client contracts subject to assignment), only their general policies. Do brokers usually provide any details of an assignment lottery upon request?