Well anecdotally I can give you four results from the UK.
My hall:
Cong 1 - This year 74, last year 101
Cong 2 - This year 98, last year 102
Cong 3 - This year 111, last year 121 (used a rented hall)
Another hall that an attendee told me about:
This year 117 last year 124.
So every hall was down and Cong 1 from my hall was a real outlier with a significant drop and no increase (in the other congs using the same hall) to compensate!