ARMFRisk diversification in trading
Risk diversification in trading came from portfolio investing: assets weakly linked to each other reduce the overall risk. On the currency market the rule works only halfway — pairs are made of the same currencies, so «different instruments» often turn out to be one bet in several guises.
Portfolio diversification: what it does and what it does not
The point of diversification is that independent positions rarely lose at the same time, so the swings of the total result are smaller than the sum of the individual swings. The key word is independent. As soon as the positions are linked, the effect disappears while the illusion of protection remains.
Three positions that are really one
The classic example of illusory diversification is buying EUR/USD, GBP/USD and AUD/USD at the same time. Formally three instruments, in fact one bet against the dollar, since the dollar stands in the quote of all three pairs.
| Set of positions | How many independent bets | Total risk at 1 % per position |
|---|---|---|
| Buying EUR/USD, GBP/USD and AUD/USD at once | 1 | about 3 % |
| EUR/USD long, USD/CHF short | 1 | about 2 % |
| EUR/USD long, EUR/USD short | 0 | 0 % and double costs |
| EUR/USD, USD/JPY, AUD/NZD — different currencies | 2–3 | about 3 % |
| EUR/USD, GBP/USD — one long, the other short | about 1 | less than 2 % |
The row with EUR/USD in both directions is not made up: this construction shows up as a «lock» instead of a stop. Economically the position is closed, but the account keeps paying the spread and the swap on both sides, while the decision to exit is simply postponed.
How to check a set of positions. Write out the currencies of all open trades and see which one appears most often and whether it is on the same side. If the dollar is on one side in every position — you have one large dollar position, and the total risk equals the sum of the risks rather than being «diversified».
Spreading risk across pairs: how many positions to hold at once
The answer follows not from portfolio theory but from two constraints: the total risk and the quality of management.
A practical reference is no more than 2–4 % of equity across all open positions, taking the links between them into account. At 1 % risk per trade that is two to four independent positions.
2–4 % in totalPositions with the same currency on the same side count as one: their risks add up rather than average out.
count the betsEvery open position requires decisions as price moves. More than four or five at once, and part of the decisions are taken in a hurry.
no more than 4–5How to count the real exposure by currency
The technique takes two minutes and replaces the argument about whether the portfolio is diversified. Each position is split into two currencies: buying EUR/USD is a long position in the euro and a short one in the dollar.
| Position | Risk | Long currency | Short currency |
|---|---|---|---|
| Buying EUR/USD at 1 % | 1 % | EUR +1 % | USD −1 % |
| Buying GBP/USD at 1 % | 1 % | GBP +1 % | USD −1 % |
| Buying AUD/USD at 1 % | 1 % | AUD +1 % | USD −1 % |
| Total on the dollar | 3 % | — | USD −3 % |
The total row is the answer: what you have is not three positions of one percent each but one bet against the dollar for three percent of the account. If the dollar strengthens, all three stops trigger together — the correlation between these pairs at such moments is close to one.
The same technique shows the opposite as well: buying EUR/USD and selling GBP/USD gives zero on the dollar, and the actual bet comes down to the EUR/GBP pair. That is already a meaningful construction — but its risk is counted on EUR/GBP too, not as the sum of two separate trades.
Frequently asked questions
Does diversification reduce risk on forex?
Only between genuinely independent positions. A set of several pairs with the same currency on the same side does not reduce risk: when that currency moves, all the positions go the same way at once.
How many currency pairs should be traded at once?
By total risk: if your limit is 3 % and the risk per trade is 1 %, that is three independent positions. The number of pairs in the portfolio can be larger, but the number of open trades is as many as fit into the limit.
Does diversification across markets help?
In normal periods, yes, between weakly linked assets. But in moments of strong moves the correlations rise: instruments that behaved independently start moving in sync exactly when the protection is needed most.
How do you know that positions duplicate each other?
Write out the currencies of all open trades and see which one repeats and on which side. Buying EUR/USD, GBP/USD and AUD/USD is three short dollar positions, that is one bet of triple size.
How many independent bets are acceptable at once?
As many as fit into the total risk limit: with a 3 % limit and 1 % risk, three. The number of open positions can be larger if the risk between linked pairs is divided.
Does trading different strategies on one pair diversify?
Partly: the trades may not coincide in time, but the market regime is shared. In a strong trend trend systems win while counter-trend ones lose — the combined result is smoothed but does not become independent.
What does adding crosses to majors give?
More independence than a set of majors with a single dollar, but also higher costs: crosses have a wider spread and a different pip value. They can be counted as independent only after checking the correlation on your own data.
Is diversification needed in intraday trading?
Less relevant: positions live for hours, and the main risk is not the link between instruments but the quality of individual entries. It is more practical to limit the number of simultaneous trades than to widen the list of pairs.
What matters more — the number of pairs or the risk size per trade?
The risk size. Five pairs at 1 % give the same drawdown as one trade with 5 % risk if the pairs are linked. Diversification changes the probability of stops triggering together, not the sum of the risks.
Does diversification reduce drawdown?
It reduces the typical swings of the account but not the maximum loss: when stops trigger at the same time, the sum of all risks is lost. That is why the total risk limit is counted by addition rather than by a dispersion formula.
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