Precisely, Rainman. A one-tooth change in cog size, corresponding to about a 4- to 7-percent ratio change, is a near-ideal ratio progression. In 1965, with a 5-speed freewheel and limited derailleur capacity, the best solution was to adopt a 2-tooth progression, and to fill in the gaps with half-step (e.g. 47-50 / 14-16-18-20-23) or Alpine/one-and-a-half-step gearing (e.g. 42-50 / 14-16-18-20-23). [Note that by swapping only the inner chainring, one can quickly change between half-step for level rides and 1.5-step for hill work, as I do on my 2-chainring road bikes.] With a 9-cog freehub, you can now obtain a decent range across the freewheel without leaving any gaps in the critical middle and high ranges, thereby eliminating the need for carefully-interlaced gear ratio progressions.