The Exchange Rate and the Market That Sets It

An exchange rate is the price of one currency in another, so it settles where the two sides meet, exactly as any price does. The awkward part is that it can be quoted either way round. One move therefore gives two different percentages, both correct, and a reader who never checks which currency sits on top will read every currency story backwards.

A price forms where willing buyers meet willing sellers, and that is as true of a currency as it is of onions. The object being priced is what differs. Nobody ever quotes onions per rupee, so an onion has one price and one direction of quotation. A currency has two directions and both are printed, in different places, on the same morning. Two printed directions generate most of the confusion in currency reporting, and the confusion is worth taking slowly rather than assuming away.

Two things already built underneath this. First, foreign money has to become local money before it can buy anything inside the country, so an inflow is a demand for the currency rather than a neutral event. Second, there are resting points that a rate may or may not sit near, one built out of goods prices and one built out of interest rates. Both are covered separately.

What is an exchange rate the price of?

An exchange rate is the price of one currency measured in another currency. The definition ends there, and every difficulty with exchange rates grows out of its second half. Because the measurement runs from one currency to another, it has a direction, and the direction can be reversed without changing a single fact.

Take the Republic of Sankhya and its partner Marut. Sankhya prices things in Sankhya rupees. Marut prices things in Marut units. The illustrative rate between them is 80.00 Sankhya rupees for one Marut unit. Written the other way, that identical rate is 0.011905 Marut units for one Sankhya rupee at the moved level and 0.0125 Marut units for one Sankhya rupee at the base, and Rs 80.00 per Marut unit and 0.0125 Marut units per rupee are the same fact, not two facts. One divided by eighty is 0.0125. Nothing has been added and nothing lost in the flip.

Ordinary life already handles this without noticing. A vegetable stall chalks up forty rupees a kilo. Nobody at the stall says twenty five grams for a rupee, but that is precisely what the board means, and if somebody did say it nobody would think the price had changed. The two countries at either end of a rate each find their own currency more natural to put underneath, so currencies are the one everyday case where both readings genuinely circulate.

So the first thing to fix is that a rate always has a top and a bottom. The currency on top is the one being counted out; the currency underneath is the one unit being priced. Stated in a full sentence every time, the problem disappears: eighty Sankhya rupees are handed over to obtain one Marut unit. Stated as a bare number, eighty, half the readers will assume the opposite arrangement and be wrong by a factor of six thousand four hundred.

What is Foreign Exchange, and who is actually in that market?

Foreign exchange is the market in which one currency is exchanged for another. The market exists for a reason that sounds too plain to be interesting and turns out to explain almost everything about it: obligations arise in currencies that the person owing them does not hold. A Sankhya importer has bought machinery and the invoice is written in Marut units. A Sankhya borrower took money abroad and the interest falls due in Marut units. A Marut investor has decided to buy Sankhya shares and the seller wants Sankhya rupees. In every case somebody holds one currency and must deliver another, on a date, in an amount that is already fixed.

Most of what crosses the foreign exchange market is not tourism, it is settlementThe act of actually handing over what was promised, in the right currency, on the agreed date. Agreeing a deal and settling it are two separate steps. of obligations that were created somewhere else entirely. The holiday money changed at an airport counter is real, and it is a rounding error beside the invoices, the interest payments and the investment flows moving through on the same day. The obligations themselves, and how they add up across a whole economy, are set out under the external accounts. The point for now is that each obligation is a person who must obtain a currency they do not have.

Who is in the market, then? Banks, mostly, acting for the people above and for each other. A bank quoting a rate is offering to act as the counterpartyThe other side of a deal. The seller is the buyer's counterparty and carries the matching obligation. for the exchange, which is why quotes exist at all: somebody is standing ready to take the other side. Add exporters and importers instructing their banks, add investors moving money in and out, and add each country's central bank, present for its own reasons. There is no single building and no bell. There is a continuous stream of quotes between institutions. A currency rate can therefore move at three in the morning, and a share price cannot.

One more consequence worth stating plainly. Because the market is made of obligations, its size on any day is not a measure of enthusiasm about a country. A large volume can be an ordinary Tuesday of invoices falling due. Reading trading volume as sentiment is a mistake that a single sentence about settlement prevents.

What Actually Determines an Exchange Rate?

Here is where most explanations go wrong, and the fault is not that they are inaccurate. The fault is that they offer a list. Interest rates, inflation, trade, growth, sentiment, central bank action. Every item on the list is real. The list as a whole is still useless. It never says which item is doing the work in the situation at hand.

An answer without a horizon attached answers nothing, so sort the determinants by the horizon each one governs. The same rate is pushed around by different things at different speeds, and the forces that explain a decade explain almost nothing about a Tuesday.

Over years, the anchor is relative prices. If the same basket of goods costs steadily more in one country than in the other once both are measured in a single currency, there is a pull on the rate. Goods can be bought where they are cheap, and the pull that follows is an arbitrageBuying something in one place and selling it in another purely because the two prices differ, which tends to pull the two prices together. in goods, and it is slow. Goods are heavy, contracts are long and habits are sticky. The arithmetic of that anchor, and the separate anchor built out of interest rates, is worked through under the two parity conditions.

Over months, the pressure comes from the external flows. A country's earnings abroad and its payments abroad both have to be settled in currency, so a persistent gap in the current accountThe running record of what a country earns from and pays to the rest of the world on goods, services, income and transfers, as opposed to what it borrows or invests. is a persistent flow of orders through the market in one direction. The external accounts, and each line inside them, are set out under the balance of payments.

Over days, the driver is nothing so dignified. Demand for and supply of the currency itself, right now, from whoever happens to be transacting, sets the rate, and a large part of that money can leave as fast as it arrived. Portfolio flowsMoney that buys listed shares or bonds without taking control of a business, and which can therefore be sold and taken out again quickly. can reverse in a week when the money behind a factory cannot. Direct money and portfolio money are separated under the two kinds of foreign money, and the distinction is worth carrying into any conversation about a single day's move.

Notice what this does to an argument. One person says the rate is pulled by prices; another says it is pushed around by investors leaving. Both speakers are right, and the two are not answering the same question. Most disagreement about a currency is two people answering correctly over two different horizons, and the fix is to make each of them name the period before either of them names a cause. A cousin who watches the rate every morning and an economist who writes about a decade will never converge, and neither of them is confused.

Why does one move give two different percentages?

Two percentages out of a single move is the awkward part, and it is worth working out slowly and in both directions at once. Take the illustrative Sankhya rate. The rate starts at 80.00 Sankhya rupees for one Marut unit and moves to 84.00. The move is one event. There is no second event hiding anywhere in it.

Work it from the Marut unit's side. The Marut unit used to fetch 80.00 rupees and now fetches 84.00. The change is 4.00, and 4.00 divided by 80.00 is 0.0500, so the Marut unit rose 5.00 per cent.

Now work the identical event from the Sankhya rupee's side. One divided by eighty is 0.0125, so the rupee used to be worth 0.0125 Marut units. One divided by eighty four is 0.011905 to six places, so the rupee is now worth 0.011905 Marut units. The change is 0.000595, and 0.000595 divided by 0.0125 is 0.0476, so the rupee fell 4.76 per cent.

The two sums do not share a denominator: the first divides by 80.00 and the second, after unwinding the reciprocalOne divided by a number. The reciprocal of eighty is 0.0125, and flipping a fraction upside down is the same operation., divides by 84.00. Both figures are correct, and neither of them is the move. That is the entire explanation. The numerator is the same 4.00 in both cases. Only the whole it is measured against differs, and it differs because one currency was placed on top in the first sum and the other currency was placed on top in the second.

If this shape feels familiar, it should. The terms of trade indexA number that compares what a country gets for its exports against what it pays for its imports, set to a base of one hundred so later readings can be compared with it. does exactly the same thing: read from one side an index moved to 110.00, and read from the other side the very same movement showed up as 90.91. One divided by 1.10 is 0.9091. For the currency, one divided by 1.05 is 0.9524, a fall of 4.76 per cent. A ratio and its reciprocal never move by the same percentage, and this is the same arithmetic showing up in a second place rather than a new phenomenon.

The worked instance, both directions at once

Numbers make this concrete faster than any argument. Suppose a Sankhya buyer has an invoice for 1,00,000 Marut units, fixed and already agreed. Suppose a Marut buyer has an invoice for Rs 80,00,000/-, equally fixed. The rate moves from 80.00 to 84.00 and both of them look at the same screen.

Read the last two rows together. The Sankhya buyer needs 5.00 per cent more rupees. The Marut buyer needs 4.76 per cent fewer Marut units. Both are consequences of the identical four rupee move. The two percentages differ for the reason already given. The rupee bill is measured against 80.00 rupees. The Marut bill is measured against 1,00,000 Marut units, and the moved rate converts it differently. Any time somebody quotes a currency percentage without naming which currency was on top, they have offered half a ratio and called it a fact.

What do appreciation and depreciation actually mean?

Two words, and no more than the words. Appreciation is what has happened when one unit of a currency now buys a larger quantity of the other currency. Depreciation is what has happened when one unit buys a smaller quantity of it. Each of those is a definition and stays one, rather than turning into a comparison.

Applied to the worked move: over the shift from 80.00 to 84.00, the Marut unit appreciated against the Sankhya rupee and the Sankhya rupee depreciated against the Marut unit. Both sentences describe the same event. Neither word carries an opinion, and neither word says whether the move was large, welcome or unusual. The contrast between the two, what each one does to different people, and how the pair behaves across more than one partner currency, is covered separately.

What can no account of an exchange rate deliver?

Everything above describes how a rate is formed and what pushes on it. None of it establishes where the rate will be. The limitation is not modesty and not a gap that better data closes. The limitation follows from the mechanism itself.

Look back at the three horizons. Relative prices are moving. The external flows are moving. Investment money is moving, and it moves partly in response to what other investment money is doing. A mechanism is not a path: an account of why a rate moves carries no claim about where it moves to. Anyone quoting a level for a future date is quoting a guess dressed in a mechanism's clothes, and the mechanism is doing the work of making the guess sound derived.

Currency talk is unusually full of confident numbers, so the point is worth being blunt about. A level for the end of next year is not an output of any mechanism. Reading a currency sentence correctly is a smaller claim than predicting one, and a more useful one.

What does an analyst check before comparing two currency numbers?

Which way the quote runs, before anything else at all. Not the size of the move, not the cause, not the commentary attached to it. Just the direction of the quotation. A percentage read off the wrong direction is not slightly wrong. It is a different quantity.

The habit is small and it costs a few seconds. When two figures for the same event arrive from two places, write each one as a full sentence with both currencies named and the word for and the word one in it: eighty four rupees for one Marut unit. Then check whether the two sentences put the same currency underneath. If they did not, the two percentages were never comparable and the disagreement was never about a fact.

The same check does real work outside a report. A shopkeeper who has bought imported stock cares about the number of rupees per unit of the other currency. Rupees per unit is the shape of the bill. An exporter's earnings arrive in the other currency and convert the other way, so the useful reading is flipped. A household paying course fees abroad wants the first reading; a worker abroad sending money back wants the second. The right reading is decided by which currency an obligation is written in, not by which one a report happened to print. Once that is settled, the same rate that looked like bad news in one paragraph and good news in another simply becomes two people describing their own bills.