At the same time, he switched from a paper strip to punched cards. (Making the cards the same size as dollar bills meant that existing storagecabinets could be used.) By clever wiring of the tabulating machine, it was possible to count the number of cards with particular combinations of attributes.
Heck, they have been talking about how computers and evolving computer storage is going to eliminate the need for paper, and my filing cabinets are still bulging.