in the case of Rohloff , lots of math went into the design , to get their 13.6% gear increase spacing ..

or each gear going downward is 86.4% of the next higher one ..

In a freewheel or cassette the tooth count difference can be bigger jumps to make the differences between lower gears larger rather than smaller ..

The reliable 3 speed uses 1 gear set in low its 3/4 of the 1:1 , and in high, its 4/3rds.. 0.75, 1, 1.33 ..