just a statistics I've gathered over openspace where I was working ~ 10 years ago - 50% or even more Windows desktops (not laptops by that time) had the same screensaver and default background which gave me a huge insight on how much customizations people really need, even for probably easiest configuration change.

For myself I count this way - 5% of population is a deviation for any given aspect - so far I think it predicts things very close.