I mean what I hear in conversations, mainly here on NP. It is widely acknowledged that most professionals sell under 5% of their portfolio per year (at the end user prices). Domains that have good keywords are easier to sell, while brandables are more difficult. I believe that BrandBucket selling rates are also around 2-3% nowadays, although used to be somewhat higher when they had less names. In any case, the percentages are only indicative, they could easily be 1%, possibly 4%, but I would be very surprised if they were 5%. At least this is my feeling, for brandable domains like this one, and for end user prices.