steve2: Unless I have missed something, the question was about numbers attending conventions, not publisher numbers.
The OP said that the trend was to have less assemblies (not less attendance)
This is FAKE NEWS.
i believe the trend is to have MORE assembly venues / dates - yes they're smaller, but number-wise they're more assemblies venue and date-wise
I await with interest how the OP backs up the claim - and as I said above, the exception is when a country holds a 'Special Convention'.
And notice how the OP's opening post has '4 likes' from forum members here - yes, that's how fake news works - it panders to confirmation bias - you make a statement, with no proof, that people want to hear, they want it to be true <sigh>
(BTW I listed the 'rounded' publisher numbers to give the number of venues some context in terms of increase, that's all - the 2017 is just the 2016 publisher figure rounded-up)