Hey forum - I've been reading through a lot of material here, and there's one question I keep coming back to. It seems to me that there are (at least) two different kinds of risk which get conflated a lot. I don't know the actual terminology for this, but let's call the two types "random" risk and "new normal" risk.
Random risk is what you get when you treat the market as a random walk or similar process - you can measure the standard deviation over a given time period, and that fluctuation gets labelled "risk".
New normal risk I'm naming after the oft-repeated saying during market crashes that "this time it's different", or "this is the new normal". It means the market has fundamentally changed, and there is no longer an expectation that past performance will be a reasonable predictor of future risk.
Another way to put it would be to go back to the random walk model. Random risk is just the standard deviation of the walk. New normal risk takes that random walk and replaces it with a completely different one with different underlying parameters.
This is relevant to me, because I have very different aversion to these two different types of risk. I'm early enough in my accumulation phase that random risk just doesn't matter much to me. New normal risk though I still do care about - if the future ends up not looking anything like the past, that's a major concern. However, we don't get to see the "underlying paremeters" for the stock market (because they don't exist), so it's difficult to tell what type of behavior you're currently seeing - is this time actually going to be different? Who knows?
Are there more official terms for these, and is this a common distinction people make? It seems like any possible deviation from "your investment will grow at exactly X% per year" gets lumped under the general heading of "risk", which I find irritating because it isn't obvious to me that the standard deviation of an investment is highly correlated with future returns not resembling past ones.
Thanks!