How Assets Move Together

Correlation is a fancy word for a simple idea: how much do two things move together?

Imagine two friends walking down the street. If they always walk side by side in the same direction, they're highly correlated. If one goes left while the other goes right, they're negatively correlated. If they wander randomly with no connection? Zero correlation.

In markets, we measure this on a scale from -1.0 to +1.0:

- +1.0 (Perfect positive): They move in lockstep. One goes up 2%, the other goes up roughly 2%.
- 0.0 (No correlation): Totally independent. Knowing what one did tells you nothing about the other.
- -1.0 (Perfect negative): Mirror image. When one rises, the other falls by the same amount.

In the real world, you'll almost never see perfect +1 or -1. Most asset pairs bounce around between 0.3 and 0.8. And here's the thing that really matters: correlations aren't fixed. They change over time, and those changes are often more important than the number itself.

Here's the thing most traders don't realize: you might think you have five separate positions, but if they're all highly correlated, you really have one giant bet.

Let's say you're long Bitcoin, long Ethereum, and long Solana. Sounds diversified, right? Three different coins. But BTC-ETH correlation is typically around 0.85, and BTC-SOL runs about 0.75. In a crash, they all drop together. You don't have three positions — you have one leveraged crypto bet wearing three different hats.

Why does this matter? Three big reasons:

1. Your risk is bigger than you think. If you sized each position assuming they were independent, your actual risk could be 2-3x what you planned for.

2. "Diversified" portfolios fail when you need them most. During the 2022 crypto crash, BTC-ETH correlation spiked to 0.95. They fell in near-perfect unison. The diversification you thought you had vanished exactly when you needed it.

3. Correlation changes are early warning signals. When assets that usually move independently start moving together, something big is happening under the surface.

In crypto, Bitcoin is the sun and everything else orbits around it. Understanding this internal correlation structure is crucial.

BTC → ETH (typically 0.80-0.90): These two move together most of the time. When BTC drops 10%, expect ETH to drop 10-15% (alts usually drop harder). The rare moments when this correlation breaks are some of the most interesting trading opportunities in crypto.

BTC → Mid-caps like SOL, AVAX (typically 0.65-0.80): Still highly correlated, but with more room to diverge. Individual catalysts (network upgrades, ecosystem growth) can temporarily decouple a mid-cap from BTC.

BTC → Small-cap alts (typically 0.40-0.65): More independent, but that independence comes with a catch — when BTC crashes hard, even low-correlation alts get dragged down. Correlations spike toward 1.0 during panic.

The altseason signal: When altcoin correlation to BTC drops below 0.6 broadly, it usually means one of two things:
- Money is rotating from BTC into alts (altseason — bullish for alts)
- Altcoins are about to catch up to a BTC move they've been ignoring (watch out)

Forex has its own correlation families, and understanding them can save you from making the same bet twice without realizing it.

Positively correlated pairs (they move together):
- EUR/USD and GBP/USD — Both are essentially "short dollar" trades. If you're long both, you're doubling your bet against the USD.
- AUD/USD and NZD/USD — Both are risk-sensitive commodity currencies from the same region. Correlation is typically 0.85+.

Negatively correlated pairs (they move opposite):
- EUR/USD and USD/CHF — Nearly mirror images (correlation around -0.90). Being long both is like betting against yourself.
- GBP/USD and USD/JPY — Often move in opposite directions, especially during risk-on/risk-off shifts.

The DXY connection: The US Dollar Index (DXY) is the gravity well of forex, just like BTC is for crypto. When DXY rises, most major pairs (EUR/USD, GBP/USD, AUD/USD) fall because you're essentially seeing dollar strength across the board.

Here's a practical tip: before you open a second forex position, check if it's correlated to your first. Being long EUR/USD and long GBP/USD isn't diversification — it's concentration.

This is where it gets really powerful. The relationships between stocks, crypto, and forex tell you about the macro environment.

Stocks vs. Crypto:
Since 2020, BTC has become increasingly correlated with the Nasdaq (typically 0.5-0.7 during risk-on periods). When tech stocks sell off, Bitcoin usually follows within hours. This correlation weakens during crypto-specific events (ETF approvals, halvings) but reasserts itself during broad market stress.

DXY vs. Crypto:
The US dollar and crypto have a mostly negative correlation (-0.2 to -0.5, depending on the period). When the dollar strengthens, it acts as a headwind for crypto. Think of it this way: a strong dollar means tight monetary conditions, which means less speculative money flowing into risk assets like Bitcoin.

Stocks vs. Forex:
The S&P 500 and risk-sensitive currency pairs (AUD/JPY is the classic one) tend to be positively correlated. When stocks rally, the Aussie dollar strengthens against the yen. When stocks crash, AUD/JPY drops as money flows from risk to safety.

Bonds vs. Stocks:
Historically, bonds and stocks have been negatively correlated — when stocks fall, bonds rally (flight to safety). But this relationship shifted in 2022 when both stocks AND bonds fell together — a reminder that the negative stock-bond correlation (which has been the norm since about 1997) is not guaranteed and can reverse. When this traditional hedge fails, it's a signal that something unusual is happening in the macro environment.

The most important correlation signal isn't the level — it's the change. Here are the patterns to watch:

Everything converging toward 1.0:
When normally unrelated assets start moving together, systematic risk is taking over. This happened in March 2020 — stocks, crypto, gold, even bonds all sold off together. When "everything correlates," individual analysis stops mattering. The macro is driving the bus.

What to do: reduce overall exposure across all markets. It doesn't matter how good your stock pick is or how bullish your crypto thesis is — a correlation-1.0 environment means everything sinks together.

Sudden decorrelation:
When assets that usually move together start diverging, one of two things is happening:
1. A genuine regime change (new narrative, new fundamentals), or
2. One asset is temporarily mispriced and will snap back

Figuring out which case you're in is where the real edge lives. Check: is there a fundamental reason for the divergence? If yes, the decorrelation may persist. If not, the reversion trade may be the play.

Crypto-specific breakdown:
When BTC and ETH correlation drops below 0.7, pay attention. It could mean ETH is leading a new narrative (like the shift to proof-of-stake), or it could mean one of them is about to catch up to the other. Either way, it's actionable information.