Been thinking about how capital moves in crypto, and it's honestly pretty predictable once you understand the pattern. Money doesn't just sit in Bitcoin forever — it rotates. Sometimes it floods into altcoins, and that's when things get really interesting for traders.

There's this metric called the altcoin season index that basically tracks exactly when this rotation happens. It measures how the top 100 altcoins are performing against Bitcoin over the last 90 days, and gives you a score from 0 to 100. Simple concept, but incredibly useful if you know how to read it.

The framework is pretty straightforward. Scores between 0 and 25 mean Bitcoin's dominating — that's Bitcoin season. Anything from 25 to 75 is neutral, nobody's really winning. But once you hit 75 and above, that's when altcoin season kicks in. At that point, most of those top 100 altcoins are beating Bitcoin, and capital is flowing hard into projects like Ethereum, XRP, and the mid-cap stuff.

What makes this index so powerful is that it's not just about individual coin performance. It's showing you where the real money is moving. When 75% or more of altcoins are outperforming Bitcoin, you know the market sentiment has shifted. That's when you see the kind of volatility that creates real opportunities — or real losses if you're not careful.

I've found that combining this with other signals like RSI or the Fear & Greed Index gives you a much clearer picture of what's actually happening. During altcoin season, the plays are obvious — increase your exposure to those mid-to-low cap coins, ride the volatility. During Bitcoin season, it's more about preservation and waiting for the next rotation.

That said, don't treat the index like gospel. Market rotations can happen fast, and not every altcoin moves the same way even when the index says it's altcoin season. External stuff like news or macro trends can throw things off. The index shows you the broad market trend, but individual coins can still surprise you.

The real edge is timing. If you can catch early signs of a rotation using the altcoin season index, you're positioning yourself ahead of most traders. That's the game in crypto — cycles are everything, and knowing when capital is about to shift between Bitcoin and altcoins can make the difference between solid gains and missing the move entirely.