Well when I work dayshifts I have to wear shoes (though I take em off a lot under my desk) and I havent ever tried to go into a store/restaurant/office barefoot so I wear something in those places as well. No clue about the percentage, but seeing how I only work 5 weekday shifts in 5 weeks (and only probably wear shoes a couple of hours during a workday) and that going to eat or shopping or dentist, etc, is only like an hour or so a couple times a week... well maybe I can approximate. Lets say work is 2hrs per weekday would average out to (2hrs x 5 weekday shifts per 5 weeks = 2hrs per week), I'll say I go out to eat once a week for 2 hrs, and into a store or other business for 3 hrs per week, thats 7 shod hours per week (168 hrs) = 95.833% barefoot, estimated.
Thats during the warmer months. For the colder months that average below freezing, I really haven't been able to go barefoot at all while outside so my barefoot % would drop significantly say November-April.