The modern understanding of corporate personhood (that "equal protection of the laws" applies to non-natural persons) is generally dated to Santa Clara County

The modern understanding of corporate personhood (that "equal protection of the laws" applies to non-natural persons) is generally dated to Santa Clara County v. Southern Pacific Railroad Company in 1888. I don't know where "94% of the lifetime of the law itself" and "inspired by British practices" come from, so I can't really dispute those.