If your portfolio holds ten different cryptocurrencies, it may still be a single bet. September 21, 2026 demonstrates the point: of the 20 non-stablecoins among the 25 largest cryptocurrencies, all 20 closed higher that day, 15 of them by at least five percent in 24 hours. Anyone who believed they were broadly diversified noticed nothing on this Monday, because everything rose at once. On a day with the opposite sign, that same lockstep becomes very noticeable indeed.
So we measured how closely the large cryptocurrencies actually move together: twelve coins, 66 pairs, 90 trading days. The detailed result is further down. The short version: average pairwise correlation stands at 0.61, and over the past 30 days it is higher than the quarterly average.
What correlation means for cryptocurrencies
Correlation is a metric between minus 1 and plus 1 that describes how evenly two prices move together. At plus 1, two coins move in perfect lockstep; at 0, their daily moves have nothing to do with one another; at minus 1, they move in exactly opposite directions. It is not calculated on the prices themselves but on daily returns, meaning the percentage changes from day to day.
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