I've updated the OP:
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.
Unfortunately, it looks like the spam reduction is already diminishing. That can be caused by the fact that last week the number of users with 1 Merit went up
25x faster than it did in previous weeks. Many Newbies were promoted back to Jr. Member, and
many of those were ranked up through Merit abuse. I also see more Newbies wearing Copper Membership now, which allows them to continue spamming their signature.