Imagine paying for something with a coin that is taller than you and weighs as much as a car. Then imagine that, after the deal is done, nobody moves the coin at all. On Yap, an island group in the western Pacific, that is how some of the most important payments have long worked. The giant stone discs used there, known as rai (and called fei by the early visitor William Henry Furness III), have fascinated economists for more than a century.
What are rai stones?
Rai stones are large, roughly circular discs of stone with a hole cut through the centre. They are also called Yapese stone money. Most are made from crystalline limestone, a pale rock that glints slightly in sunlight, and they range from the size of a dinner plate to giants several metres across.
The largest known examples are about 3.6 metres (12 feet) in diameter and are often said to weigh around 4 tonnes. A survey carried out in 1929, when Yap was under Japanese administration, counted roughly 13,000 stones. Many were lost or destroyed in the decades that followed, and while modern estimates vary, several thousand large stones remain on Yap today. A number have also found their way into museums around the world.
Yap is now part of the Federated States of Micronesia, a country that uses the US dollar for everyday shopping. The stones, however, have never entirely disappeared from island life.
Where did the stone come from?
Here is the first surprise: Yap has no suitable stone of its own. The limestone was quarried on other Micronesian islands, chiefly Palau, which lies roughly 400 kilometres (about 250 miles) to the south-west.
Yapese voyagers would sail to Palau, carve the discs with simple tools, and bring them home by outrigger canoe or on rafts towed behind. The hole in the middle allowed a stone to be slung on a wooden pole and carried by a team of people. Crossing open ocean with a multi-tonne slab of rock was genuinely dangerous, and some voyagers never returned.
Exactly when this tradition began is unknown. Its origins survive mainly in Yapese oral legends, and historians are not certain how many centuries the stones have been in use.
What made one stone worth more than another?
Size mattered, but it was far from the whole story. A stone's value also depended on:
- Its history: who had owned it, and in which important exchanges it had changed hands.
- The effort behind it: how hard the quarrying and voyage had been.
- The risks involved: stones linked to a perilous crossing, or to lives lost at sea, could be especially prized.
- Craftsmanship: the smoothness and shape of the disc.
In other words, a rai stone was valuable partly because it carried a story the whole community knew. That shared knowledge turns out to be the key to the whole system.
Money that stays put
Because the biggest stones are so heavy, and moving them risks cracking them, they were usually left exactly where they stood. When a stone was used as payment, it was the ownership that moved, not the rock. Everyone in the community simply knew, and remembered, that the stone now belonged to someone else.
Economists often compare this to a ledger, a record of who owns what. On Yap the ledger was not written down; it lived in collective memory and was passed on through spoken history. Modern writers frequently liken it to a blockchain, the shared digital record behind cryptocurrencies, though the comparison is a loose one.
Yap also has places known as stone money "banks", where many discs stand together in rows. They are not banks in the modern sense, but displays of wealth gathered in one spot. One of the best known is at Balabat, near Colonia, the island's main town.
The stone at the bottom of the sea
The most famous rai story was recorded by Furness, an American anthropologist who visited Yap and published The Island of Stone Money in 1910. He described a family whose ancestor had obtained an enormous stone on Palau. On the journey home, a storm struck and the stone sank to the seabed.
The crew all agreed that it had been a magnificent stone and that its loss was no fault of the owner. So the islanders accepted that the stone still existed, even though nobody alive had ever seen it. The family remained wealthy, and the sunken stone could still be used in exchanges like any other.
To an economist, this is remarkable. It shows that the stone's value never depended on anyone being able to touch it. It depended on everyone agreeing that it existed and who owned it.
A trader, a ship and too many stones
In the 1870s an Irish-born American sea captain named David Dean O'Keefe arrived on Yap. He realised he could use his ship and iron tools to carry rai stones from Palau in far larger numbers than canoes ever could, and he traded them with islanders for goods such as copra (dried coconut) and sea cucumbers.
The stones he brought were widely regarded as less valuable than traditionally made ones. They had been obtained with little danger or effort and lacked the stories that gave older stones their worth. Many writers see this as an early, real-world example of how flooding an economy with new money can erode what each piece is worth, an idea economists link to inflation, the general fall in money's buying power.
Furness also reported that when German colonial officials governed Yap around 1900 and wanted villages to repair their roads, they painted black crosses on stones to show they had been claimed as fines. The work was done promptly, and the crosses were then removed. Nothing physical had moved, yet the threat to people's wealth was entirely real.
Why economists still talk about Yap
In 1991 the Nobel Prize-winning economist Milton Friedman wrote a short paper titled "The Island of Stone Money". He used the sunken stone and the German painted crosses to make a point about modern money, and set them beside an episode from the early 1930s.
In 1932 France, fearing the US dollar would fall in value, asked the Federal Reserve Bank of New York to convert its dollar holdings into gold. The gold never left the building: staff simply set it aside in the Fed's own vault and labelled it as French. Yet American newspapers reported a "loss of gold", and that alarm helped feed the banking panic of 1933. Was a relabelled bar of gold, Friedman asked, really so different from a painted cross on a stone?
The lesson is that money is ultimately a matter of shared trust. Banknotes are just paper, and most of the money in a modern bank account exists only as numbers in a computer system. Like rai stones, they work because enough people believe they will be accepted by others.
Today rai stones are no longer used for buying groceries, but they still play a part in traditional exchanges on Yap, such as marriages, settlements and some land arrangements. They stand as a quiet reminder that the strangest-looking money in the world may be the one that explains our own best.
