Given that, at least in the US, people had to regularly sue corporations that defend the secrecy of their fancy algorithms^W^W Excel sheets as trade secrets... that's not as obvious as you might think.
Why would that be? Health care providers, bail risk assessment software for courts, ... it's not like some public entity like the IRS would be likely to develop much in-house.
Given that, at least in the US, people had to regularly sue corporations that defend the secrecy of their fancy algorithms^W^W Excel sheets as trade secrets... that's not as obvious as you might think.