Stock market volatility is back

Remember volatility? Well, it's back. Take a look, for instance, at the last three months of the Dow Jones Industrial Average.

Between Aug. 17 and Oct. 9, the average daily range — the difference between the intraday high and the intraday low — was 177 points. Between Oct. 10 and Nov. 16, the average daily range was 455 points, 2.5 times greater.

Why you’ll hear about this again: 400- or 500-point days on the Dow are normal, these days, and they almost always happen for no particular reason.

Other asset classes are seeing a similar failure, on the part of markets, to come to a stable consensus on what they're worth. We've already talked about oil, so let's take a look instead at cryptocurrencies.

• In just the past week, bitcoin is down 13%, ethereum is down 18% and bitcoin cash (don't ask) is down 30%.

Volatility tends to mean big drops more than it does big rallies. Chipmaker Nvidia has lost almost half its value since the beginning of October, Apple has lost almost $200 billion in capitalization over the same time, J.C. Penney looks like it might drop below a dollar per share, and California wildfires have poleaxed the stock of PG&E.

Be smart: Insofar as you can, it's worth tuning out this noise. The markets have been weirdly, puzzlingly quiet for a couple of years now. In a world where unknowns abound, it makes sense that valuations would be very hard to pin down.