clayop and someone else did a study a week or two ago and came up with that number. it can only be approximated because nobody knows exactly which accounts are bots but it isn't surprising when you look at most of the top stakeholder and curator accounts by amount, most are not bots, they are either human curators or guilds (blocktrades, val, michael, dan, abit, ned, etc). You are paying too much attention to number of votes, and yes there are many small bot accounts/votes, but that isn't what matters.