Correlatie en diversificatie: waarom risico spreiden vaak niet genoeg is

This is an education piece, not a pitch. The goal is to give you a way to check whether your open trades are genuinely independent or secretly the same trade wearing different names.

What does correlation actually mean for a trader?

Correlation measures how closely two prices move together, on a scale from +1 to -1. A correlation of +1 means they move in lockstep; -1 means they move exactly opposite; 0 means they are unrelated. It is a description of behaviour, not a promise, and it drifts over time, which is precisely what makes it dangerous.

The number matters because risk does not add up the way position counts do. Five uncorrelated trades really do spread risk. Five trades that all rise and fall together are, in risk terms, one position at five times the size. The account feels diversified and behaves like a single leveraged bet.

Why can five open trades still be one bet?

Because instruments that share a driver move as a group. Consider a trader who is long gold, long silver, long EUR/USD, long GBP/USD and short the US dollar index. That feels like five ideas. In reality it is one idea: "the dollar falls." If the dollar rallies on a strong jobs report, all five lose at the same moment, and the combined drawdown is far larger than any single line suggested.

Each row looks like two or three positions and behaves like one. The lesson is not "never hold correlated trades." It is that when you do, you must count them as a single risk and size them accordingly rather than pretending each is independent.

How do you measure whether your trades are truly diversified?

Group your open positions by their underlying driver, not by their name. Ask a blunt question of the whole book: "If the dollar moved 1% against me right now, how many of these lose at once?" If the answer is "most of them", you are not diversified, no matter how many symbols are on the screen.

A simple, honest check for a retail trader has three steps. First, list every open trade and write down the one macro force that most affects it (the dollar, real yields, risk appetite, the oil price). Second, tally how much total risk sits behind each force. Third, treat any single force carrying more than your per-trade risk limit as a concentration to reduce. This costs nothing and catches the trap that formal statistics would also flag. For the downside it protects you from, see what drawdown really measures, because correlated losses are exactly how a shallow-looking strategy produces a deep drawdown.

Does diversification reduce return as well as risk?

Yes, and any honest article has to say so. Genuine diversification lowers the volatility of your results, and in doing so it also caps the explosive upside of being concentrated in the one thing that happens to fly. You cannot get the smoother ride and the lottery ticket at the same time. What diversification buys is survivability: a portfolio that does not depend on a single macro call being right.

There is also a limit worth knowing. In a genuine crisis, correlations tend toward +1, meaning things that were independent in calm markets fall together in a panic. That is why professional risk management leans on position size and drawdown limits, not diversification alone. This is the same discipline behind judging any strategy on a long, independently verified record rather than a good month, which is why TIC publishes its verified Myfxbook results at /results and why the honest way to read one is covered in backtest versus live results.