Sometimes banks get in trouble with regulators for misconduct, and the regulators fine the banks and issue an order describing the misconduct, and I read a description of the misconduct and am like “ah yes that sounds like misconduct.” Other times, I read the description and am like “hmm I guess but that’s kind of a gray area and I can understand why they thought it was allowed.” (Perhaps this is just me.) But sometimes, I read the description of the misconduct and am like “well that’s just using a computer, that’s just how computers work, anyone would mess that up, you can’t blame them for that.” Of course there the misconduct is in designing the computer system in such a way that people will inevitably mess it up.

For some reason, that sort of misconduct seems to happen a lot at Citigroup Inc. In 2021, Citi accidentally sent $900 million to some angry hedge funds because of what I called “a gothic horror story about software design.” Today the UK’s Financial Conduct Authority and Prudential Regulatory Authority fined Citi £61.6 million ($79 million) for a 2022 fat-finger stock trade that happened like this: