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 ...
XYM Distribution Thu, 25 Mar 2021 18:37:26 UTC
Top Accounts XYM Percentage
Top 50 5,361,690,941.63 68.3%
Top 100 5,863,290,975.49 74.7%
Top 200 6,181,400,266.32 78.8%
Top 250 6,332,191,891.12 80.7%
Top 500 6,925,022,099.09 88.3%
Supply 7,846,691,959.02 100%
The XYM Distribution seems to be more concentrated than XEM's. Maybe the reason is in the "passive NEMbers", who may have forgotten their XEM accounts or not yet made the opt-in.