There are roughly one hundred and eighty national currencies, and almost none of them matter to
anyone outside their borders. A handful carry the world's trade, and one carries most of it.
The one thing to remember: an exchange rate is a price, and like every price it
is set by people acting on what they expect. Even where a state fixes one by decree, it is
holding a price against that pressure rather than choosing it freely; a rate can sit in the
wrong place for years.
What makes something a currency
Three things, mostly. A government declares it legal tender for settling debts. The state accepts
it, and usually only it, for taxes, which guarantees a permanent demand. And enough people use
it as the unit they think and price in that it becomes the natural way to keep accounts. The
third is the one that cannot be legislated, which is why a currency people have stopped trusting
can be legal tender and still be refused in a market.
The international standard for currency codes, ISO 4217, lists somewhere around one hundred and
eighty active codes; the exact number moves as countries adopt, redenominate and abandon
currencies. That figure is worth holding loosely.
Six ways to run an exchange rate
Regimes run from complete monetary independence to none at all. Every one trades stability
against control.
Regime
How it works
Examples
What it costs
Free float
The rate is whatever the market clears at; the central bank rarely intervenes.
US dollar, euro, yen, sterling, Swiss franc, and most large advanced economies.
Volatility. Importers and exporters must hedge or absorb the swings.
Managed float
Market-determined, but the central bank leans against moves it dislikes.
Many large emerging economies.
Requires reserves, and invites arguments about currency manipulation.
Crawling peg
A fixed rate that is adjusted on a schedule, usually to track an inflation differential.
Used periodically across Latin America and Asia.
Predictable to the point of being a target for speculators.
Hard peg / currency board
A fixed rate defended by a legal commitment, with domestic money fully backed by foreign reserves.
Hong Kong’s dollar has been pegged to the US dollar since 1983.
You import the anchor country’s monetary policy whether or not it fits your economy.
Dollarisation
Use another country’s currency outright and abolish your own.
Panama has used the US dollar for over a century; Ecuador adopted it in 2000 and El Salvador in 2001.
No monetary policy at all, and no lender of last resort in your own money.
Monetary union
Share a currency and a central bank with other countries.
The euro area; the two CFA franc zones in West and Central Africa.
One interest rate for economies that may need different ones: the central tension of the euro crisis.
The euro is the largest deliberate experiment in the last category. It began on 1 January 1999 as
an accounting currency for eleven countries, with notes and coins arriving on 1 January 2002.
Croatia joined on 1 January 2023, taking the euro area to twenty members, and further accessions
have followed; the European Central Bank's own list is the authority, and it is linked below.
What actually moves a rate
Five drivers. Over years the first two dominate; over days the fourth does.
Driver
Effect
Interest rate differences
Money moves toward higher real returns, pushing that currency up until the move itself makes the return unattractive.
Inflation differences
A currency losing value at home tends to lose it abroad. This is the long-run anchor behind purchasing power parity.
Trade balances
Persistent deficits mean persistent selling of the currency to buy foreign goods, though capital flows now dwarf trade flows in daily volume.
Capital flows and risk appetite
In a panic, money runs to whatever is considered safest, which usually means the dollar, even when the panic started in America.
Policy credibility
Markets price the expectation that a central bank will do what it says. Losing that is expensive and slow to regain.
Purchasing power parity is the long-run tether: if a basket of goods costs far more in one
country than another once converted, there is pressure for the rate to close the gap. It is a
real force and a terrible short-term predictor: rates can sit thirty percent away from it for a
decade. The Economist's Big Mac index, published since 1986, exists to make that point
memorably.
The dollar’s position, in numbers
The Bank for International Settlements surveys the foreign exchange market every three years.
In April 2025 average daily turnover reached 9.6 trillion dollars, up roughly 28 percent from
7.5 trillion in April 2022. The US dollar was on one side of about 89 percent of all trades; it
has sat between 88 and 90 percent in every survey for three decades, and the 2022 round put it
at roughly 88 percent. The euro is a distant second at under a third, the yen third at around a
sixth. Because every trade has two currencies, the shares total two hundred percent, not one
hundred. The exact figure for each survey year is in the BIS tables linked below; read those
rather than any rounded number here, including these.
Reserves tell a slower version of the same story. The IMF's COFER data has shown the dollar's
share of allocated official reserves drifting down over two decades, from around seventy percent
at the euro's launch to something closer to the high fifties in recent readings, with the euro a
distant second. That is a real decline and it is not a collapse: no other currency is close to
taking the role, and the slide has been slow enough to measure in decades.
Holding the world's reserve currency is a mixed inheritance. It lowers a country's borrowing
costs and lets it settle its own imports in its own money. It also means foreign demand for your
currency is driven by other people's needs, which was the tension Robert Triffin identified in
the 1960s: the world wants more of your money than your own economy would issue.
Why money crosses borders
Four main reasons. Trade: goods bought in one currency and sold in another. Investment: capital
seeking a return abroad. Reserves: central banks holding foreign assets as a buffer. And
remittances (migrants sending money home), which for many low- and middle-income countries is a
larger and far steadier inflow than foreign aid, running in recent years at a global scale of
several hundred billion dollars a year.
Remittances are also where ordinary people meet the foreign exchange market at its worst. The
cost of sending a small sum across a border has been stubbornly high: the global average has
hovered around six percent of the amount sent, against a United Nations target of three percent.
On a hundred dollars sent monthly to a family, the gap between six percent and three percent is
about thirty-six dollars a year. That is a rounding error in the abstract, and not a rounding error to
the household receiving it. If you send money abroad, compare the total cost including the exchange rate
margin, which is where most of the charge usually hides.
Scripture, trade, and the money changers
The Bible is comfortable with international commerce and unsentimental about it. Ezekiel's lament
over Tyre is essentially a shipping manifest: silver, iron, tin and lead from Tarshish, slaves
and bronze from Javan, horses from Togarmah, and on for pages. Trade is portrayed as real wealth
creation and as a spiritual danger to the trader, both at once.
12“‘“Tarshish was your merchant by reason of the multitude of all kinds of riches. They traded for your wares with silver, iron, tin, and lead. 13“‘“Javan, Tubal, and Meshech were your traders. They traded the persons of men and vessels of brass for your merchandise. 14“‘“They of the house of Togarmah traded for your wares with horses, war horses, and mules. 15“‘“The men of Dedan traded with you. Many islands were the market of your hand. They brought you horns of ivory and ebony in exchange. 16“‘“Syria was your merchant by reason of the multitude of your handiworks. They traded for your wares with emeralds, purple, embroidered work, fine linen, coral, and rubies. 17“‘“Judah and the land of Israel were your traders. They traded wheat of Minnith, confections, honey, oil, and balm for your merchandise. 18“‘“Damascus was your merchant for the multitude of your handiworks, by reason of the multitude of all kinds of riches, with the wine of Helbon, and white wool. 19“‘“Vedan and Javan traded with yarn for your wares: bright iron, cassia, and calamus were among your merchandise. 20“‘“Dedan was your trafficker in precious cloths for riding. 21“‘“Arabia, and all the princes of Kedar were the merchants of your hand; in lambs, rams, and goats. In these, they were your merchants. 22“‘“The traders of Sheba and Raamah were your traders. They traded for your wares with the chief of all spices, and with all precious stones, and gold. 23“‘“Haran, Canneh, and Eden, the traders of Sheba, Asshur and Chilmad, were your traders. 24These were your traders in choice wares, in wrappings of blue and embroidered work, and in chests of rich clothing, bound with cords and made of cedar, among your merchandise. 25“‘“The ships of Tarshish were your caravans for your merchandise. You were replenished and made very glorious in the heart of the seas.
An ancient trade map in verse. The point of the passage is not that trade is wicked (Tyre's commerce is described with something close to admiration) but that a city which becomes its own idol will sink with its cargo. Read the whole chapter for the reversal.
The money changers in the temple are often quoted as a verdict on currency exchange. They are
not. Pilgrims arriving for the feast carried the coin of a dozen provinces and needed acceptable
coinage for the temple tax and for buying sacrifices, so exchange was necessary. What Jesus
condemns in Matthew 21:12-13 is what the trade had done to the place: a house of prayer turned
into a market, and the pilgrims (especially the poor buying the cheapest offering) with nowhere
else to go. The sin named is the exploitation of captive worshippers in a holy place, not the
business of changing one currency for another.
Alongside that, Scripture keeps returning to the foreigner. Israel was told repeatedly to love
the stranger, because they had been strangers in Egypt (Deuteronomy 10:17-19). Anyone building
products that charge migrants to move their own wages should read that passage before setting
the fee.
Weighed by the Book
CommandedWhat Scripture commands
Use a just weight and a just balance, which includes a fair rate and disclosed fees (Leviticus 19:35-36; Proverbs 11:1).
Love the stranger and do not oppress him, because you were strangers yourselves (Deuteronomy 10:17-19; Exodus 22:21).
Do not exploit people in a place or situation where they cannot walk away (Leviticus 25:14; Leviticus 19:13); the temple traders of Matthew 21:12-13 are the narrative case.
WisdomWise application, not command
Hold your emergency money in the currency your bills arrive in. Currency mismatch is how households get hurt in a devaluation.
Currency trading is a zero-sum market populated by institutions; treating it as an investment is speculation with extra steps.
When sending money abroad, compare total cost, not the advertised fee; the exchange rate margin is usually the bigger charge.
FreedomWhere faithful people differ
Whether a country should float, peg or dollarise is an economic and political judgement Scripture does not make.
Holding some savings in a foreign currency may be prudent or unnecessary depending entirely on where you live and what you owe.