Yep and this is because for instance, to be listed on the dow jones one needs to meet certain criteria and when you don't, you're unlisted and replaced. If you look at how many companies have been replaced on that index, you'll see it has collapsed over and over again since it's inception. That's why it's always creeping up, losers are quietly replaced by a mover.More correctly, it is stock index values that have an upward bias, not individual stocks.
So, when you see a crash it's really worse than we realize, because stocks can't even be replaced fast enough.