Stock market down - pension money goes in - stock market goes up - profits (worker pensions) are taken - market goes down.
Now I will sit back and wait for those much smarter than me in these matters to reply.
Understand, you don't know, something unless you're betting heavily on it. If everyone's betting heavily on it, there's no one else to put money in. When that happens, there's nothing to keep the prices up.
The same thing happens in reverse, in a recovery.
Maybe now? (If I knew, I could make a fortune couldn't I?)