ARKUSDT
Ark / Tether USD
cryptoComposite

Sort of, but I think we are talking about different things and I see your point. The OP asked, "Why ISN'T past performance an indicator of future returns". I assumed they are asking purely based on math (IE will tomorrows price be affected by todays price). Look at something like ARK invest from inception until Feb 2021. Their trend line across that time frame had a CAGR of positive 37.4%. If you go from Feb 2021 to today, its...... negative 8.7% per year. A delta of over 45%. Other funds did in fact maintain or even beat 30% CAGR over that period, so the previous or preexisting trend by itself does not explain anything. You could say that's just one stock, but wildly different inflation adjusted trends over long time frames also exist for entire stock markets. What I mean is, any trendline was developed based on arbitrary pre existing end points that you selected, there is nothing about past price performance that indicates a reversion to the historic mean will continue over as of yet unknown future time frames and future end points without also assuming the cause of that trendline also persists. Maybe this is where we are talking about different things (or the same thing?). There is of course momentum across large industries and countries, if you mean to say such momentum can continue for a while, I agree, but only because the fundamentals also continue. A line means nothing if the cause of that line stops functioning but maybe this is what you mean.

ARK