What is the carry trade — earning on the interest-rate differential

Imagine someone crediting a few cents to your account every night simply because you are holding a position open. That, in short, is the carry trade — a strategy in which you hold the higher-yielding currency, fund it with the lower-yielding one, and collect a positive swap point each day. It sounds like money for nothing, which is exactly why capital flowed into pairs such as AUD/JPY. The catch is that this is the same mechanism that, in August 2024, erased months of accumulated profit in a matter of days. Below I explain how the carry trade really works and why it is no free lunch for a beginner.

What the carry trade actually is

The carry trade is a strategy built on the interest-rate differential between two currencies. You hold a long position in the currency that pays the higher rate and, through the structure of the currency pair, a short position in the currency that pays the lower one. Every day, as the position rolls over to the next session, the broker credits a swap point that reflects that gap. This swap credited to the account is the carry itself: income from merely holding the position, independent of whether the exchange rate has moved.

The key is to separate two sources of result. The first is the price change — the ordinary difference between the opening and the closing price. The second is the carry, the accumulated swap points. In a pure carry trade you are counting mainly on the second: you want the pair to stand still or drift gently in your favour while the swap slowly drips into the account. That is what distinguishes the carry trade from directional speculation, where the whole profit is meant to come from the price move. Here, patiently holding the position is part of the plan rather than the result of indecision.

How the rate gap turns into swap points

The swap is not a gift from the broker — it is a product of how the forward market is priced. When one currency pays 4 percent and the other 0.1 percent, the forward contract on that pair has to reflect the gap, otherwise a risk-free arbitrage would exist. That relationship is described by interest-rate parity, and in practice it reaches your account as an overnight swap point. I broke the settlement mechanics down in a separate piece on what a forex swap is, and the theory behind it in the article on interest-rate parity.

There is a catch that is easy to forget, though: the broker keeps part of that differential as its margin. The raw rate gap might be 4 percentage points a year, but the swap you actually receive is smaller, because the broker adds its own mark-up. When the differential is large, the mark-up is bearable. When it is small, it can swallow most of the positive carry, and in an extreme case both sides of the position pay a negative swap. So before anyone calls a pair "carry-positive", they should check the real swap at their own broker rather than the headline rate gap.

The classic examples: cheap yen, costly dollar

The best-known carry trade of recent years was a long position on AUD/JPY. For years the Bank of Japan held rates near zero while the Reserve Bank of Australia paid markedly more, so buying the Australian dollar with the yen produced a positive swap. Going long on USD/JPY worked the same way over 2022 to 2024, when the Federal Reserve raised rates aggressively while the Bank of Japan stayed close to zero. The rate gap between the dollar and the yen widened so far that the yen became the funding currency of choice for the whole market.

This is the general mechanism of the carry trade — not the profile of a single pair. If you want to see how it looks on one concrete example, complete with figures and the context of Bank of Japan policy, I set it out in a separate article on the USD/JPY carry trade. Here my aim is the principle: the carry trade always works the same way — you borrow the low-rate currency cheaply and put the money into a higher-rate one. Only the pairs and the rate levels change, and those depend on central-bank decisions, which are worth following, for instance through a watch on Fed, ECB and Bank of Japan policy.

"Carry traders are subject to crash risk: exchange rate movements between high-interest-rate and low-interest-rate currencies are negatively skewed." — Markus Brunnermeier, Stefan Nagel, Lasse Pedersen, *Carry Trades and Currency Crashes*, NBER, 2008.

The risk that is easy to overlook

This is where the part you never see in the "earn on the swap" pitch begins. The carry trade is leveraged, and leverage magnifies not only the positive swap but the exchange-rate risk too. The swap you collect is small — measured in fractions of a percent a day. The price move can be large — a pair can shift in a single day by as much as you would accumulate in swap over many weeks. That asymmetry runs against you: a slow, thin stream of income set against rare but violent capital losses. Brunnermeier and his co-authors call this negative skewness — long stretches of calm, small gains punctuated by sudden collapses.

The hardest lesson of recent years was the yen carry unwind in early August 2024. According to the analysis by the Bank for International Settlements, the scale of yen-funded positions reached roughly 40 trillion yen going into the event, around 250 billion dollars. When the Bank of Japan signalled tightening and a weak US labour-market reading fanned fears about the American economy, investors began closing those positions all at once. On 5 August 2024 the yen appreciated the most, while high-yielding investment currencies such as the Mexican peso fell hard. Rising margin requirements forced still more closures — a textbook cascade.

Consider a hypothetical, illustrative example. An investor holds a leveraged long position on AUD/JPY and, for half a year, patiently collects a positive swap, crediting modest but regular amounts to the account. Then come five sessions like those at the start of August 2024 — the yen appreciates by several percent, leverage multiplies that move, and the loss on the rate exceeds the entire swap accumulated over six months. This is not a doomsday scenario plucked from thin air; it is exactly the kind of episode the BIS documented on real data. Carry works right up until it does not — and it stops working abruptly.

An honest verdict — is it worth it

The carry trade is neither a scam nor magic. It is a real strategy that large players use too, and the positive swap genuinely lands in the account every night. But it is no free lunch for a beginner, because the income from the rate gap is small against currency volatility, and leverage sharpens that imbalance. Worse, the unwinds are correlated: in a panic every carry trade collapses together, so holding several "carry-positive" pairs at once does not diversify the risk, it compounds it. The swap stream looks like calm income right up to the day it stops being one.

The practical takeaway is this: treat the positive swap as a pleasant add-on to a position you wanted to open for directional reasons anyway — not as the sole reason to hold it. If the only argument for a position is "because they pay me the swap", you are probably underrating the exchange-rate risk on the other side. For a broader treatment of the carry trade and the funding-currency dynamic, see the carry trade glossary entry on forexmechanics.com.

What to do tomorrow

1. Check the real swap at your own broker before you call a pair "carry-positive". Open the instrument specification in your platform and read the long and short swap points for the pair tempting you. Compare them with the raw rate gap from the headlines — you will often find the broker mark-up eats most of the positive carry, at which point the whole calculation loses its point.
2. Work out how many days of swap a typical price move on your pair erases. Take the daily swap in your account currency and divide it by what you earn or lose on a one-percent move in the pair. The answer — usually many weeks or months — will show you in black and white how small the carry income is against the exchange-rate volatility.
3. Open a test position on a demo account and hold it for a week. Watch with your own eyes how the swap credits each night and how a single larger price move can outweigh the whole week of carry in one day. The exercise makes real the asymmetry you cannot feel from a table of numbers alone.
4. Note the dates of the next central-bank decisions for both currencies in the pair. Put the meetings of the funding-currency and the investment-currency central banks in your calendar — it is a change, or even just a signal of a change, in rates that most often triggers a violent carry unwind. Knowing those dates is the difference between being surprised and being prepared.