The one exact math, which is every time forgotten, is the fact that when someone sells, then also someone buys.
According to the distribution list changes the big owners have not sold. Of course some of them have sold, but in the big picture they have not sold, because the Top100 has increased their ownings from 57 %   to   71 %.  


Distribution Fri, 05 Jan 2018 18:33:44 UTC:
Top Accounts           XEM                                         Percentage
Top 50                    4,804,818,406.12                         53.4%
Top 100                   5,119,481,371.59                         56.9%
Top 200                   5,455,792,305.26                       60.6%
Top 250                   5,609,101,108.18                       62.3%
Top 500                   6,365,621,548.69                       70.7%
All                           8,999,999,999                         100%




Distribution Fri, 12 Mar 2021 05:39:36 UTC:
Top Accounts           XEM                                         Percentage
Top 50                    6,166,236,694.24                       68.5%
Top 100                   6,423,452,170.92                         71.4%
Top 200                   6,739,353,256.10                       74.9%
Top 250                   6,890,203,307.06                         76.6%
Top 500                   7,543,466,571.50                       83.8%
All                           8,999,999,999                           100%



That may be mainly caused by the exchanges' accounts (people have moved their XEMs there...), but still: the Top100 individual owners have not sold much of their ownings. Now can easily be detected only 3 names whose accounts have been "emptied": mixmaster, bogdana and rockethead.

There may be different reasons: transferred to 3 MXEM nodes to harvest, or to exchanges to trade. Or to exchanges to ensure the XYM airdrop instead of "not-so-working-XYM-wallet-in-own-computer". Or to exchanges to sell some to cover the expenses of life. The last is the reason for some, no need for examples ...