What altseason means, measured rather than assumed

The published index declares altseason at a reading of seventy-five or above, meaning at least three quarters of the tracked universe outperformed Bitcoin over the trailing ninety days. Nothing structural happens at that number. It is a round figure chosen because three quarters reads as "most", and a market reading seventy-one is not meaningfully different from one reading seventy-six. Treating the crossing as a signal rather than as a description is the most common error made with the measure.

The window is a second convention. A ninety-day lookback is long enough to smooth daily noise and short enough to describe a season, but it is backward-looking by construction. By the time a reading crosses the threshold, the rotation it describes has already been running for weeks. The index confirms that a period of broad outperformance occurred; it does not identify the start of one, and it cannot be used to time an entry.

The universe is a third. The top-fifty and top-hundred versions of the same construction can print different readings on the same day, because a wider universe pulls in smaller and more volatile names that behave differently from the largest assets. Neither is wrong; they are different samples answering the same question. A reader who wants to use any of these measures should therefore state which universe and which window they mean, because "altseason" without those two qualifiers is not a measurement at all.

The first limitation is that all three measures are relative. They compare altcoins with Bitcoin, so a reading tells you about the division of the market rather than about its direction. A market in which everything fell, and Bitcoin fell most, will register as altseason on the breadth measure. A reader who takes the label as a statement about profitability has misread it.

The second is survivorship. A universe defined as the top fifty assets today is not the top fifty of three years ago. Assets that collapsed out of the index are absent from the current reading, and assets that grew into it are present. That makes historical comparisons of the index less clean than they appear, and it is a reason to treat any long-run claim built on the index with caution.

The third is the distinction between co-movement and cause. A reading of seventy-five says that three quarters of a universe outperformed Bitcoin over a window. It does not say that Bitcoin's behaviour produced that outcome, and it does not identify the mechanism. The capital rotation page sets out what evidence would be needed before a rotation explanation could be preferred to a common-factor one, and the timing page tests whether the episodes lined up with Bitcoin's peaks.