[steveax]

Yeah, 5.10a -> 5.10b is about the same step up as 5.7 -> 5.8 and the Yosemite Decimal System was indeed developed somewhere other than Yosemite: Tahquitz/Suicide in Southern CA [1] (where many of the golden age climbers and stonemasters honed their skills)

[1]: https://en.m.wikipedia.org/wiki/Tahquitz_Peak

[justinator]

My suggestion is that it's not. I would be very curious on how one can empirically prove this.

[steveax]

Since the grades are subjective, and largely determined by the first ascentionists, (although through consensus sometimes re-graded) this is not possible. My subjective take on it, up to 5.11+, can't speak for anything beyond that, is that a bump in a grade, any grade is about the same increase in difficulty. My climbing has mostly been in Joshua Tree, Idyllwild, Smith Rocks and a bit in the valley.