Registration count differs from table stats to user.joindate

[ub.ch]

Heya

I have a weird phenomenon:
If I look up the new registrations in the AdminCP using Statistics & Logs -> Registration Statistics the total count for a year (eg counting all rows) is 18'120

If I then search in Users -> Join Date is After & Join Date is Before (same period), the total number is 9'379
Sort of the same if I do an manual query:

PHP Code:

select count(*) from user where joindate >= 1514761200 and joindate < 1546297200 

Can anyone explain why they are off by nearly half?!

Best
Malte

--------------- Added [DATE]1548678973[/DATE] at [TIME]1548678973[/TIME] ---------------

Ah forgot to mention: of course there are some deleted users, but I've never deleted 9k of them!