Yeah, I wasn't thinking of that when I started this thread, but I know that the financial reports usually do specify "Dow Jones industrial average" ( or "S & P" or NASDAQ).   I just never had a good anchor on what a drop of, say, 100 points or 300 points or a rise of a few hundred points meant.   I was never sure what sort of scale it was.

Today they're talking about a 700-point drop as one of the worst ever.   OTOH, it seems the indexes (indices?) can vary widely within a single day - as happened today.