In 24 hours, that's 23.3% less posts.
In 48 hours, that's 18.6% less posts.
In 1 week, that's 15.9% less posts.
In 2 weeks, that's 18.6% less posts.
OP updated.
I'm happily surprised to see the reduction go up again.
If I ignore the one week before and after theymos' changes, and only look at the number of posts made a week earlier and later (so posts made from September 3 to September 10, and from September 24 to October 1), it went down from 355933 to 280633 posts. That's a 21.2% reduction.