There is a certain irony in the fact that some of the most rigorous economics departments and central banks on the planet, institutions built on regression models and decades of monetary theory, regularly cite a burger.

Not metaphorically. Literally. The price of a McDonald’s Big Mac, in local currency, converted into US dollars, sits in the same conversation as inflation data, interest rate decisions and GDP forecasts. It has its own Wikipedia entry, its own dataset maintained on GitHub and its own economic sub-discipline with a name: burgernomics.

This is the story of the Big Mac Index – where it came from, how it actually works and why a magazine’s light-hearted joke from 1986 refused to go away.

A joke that got out of hand

The index was dreamed up by Pam Woodall, an economics journalist at The Economist and first published in September 1986. The idea began, by most accounts, as a way to make a genuinely dry concept – purchasing power parity – digestible to a general readership. Rather than parade a basket of abstract goods and services in front of readers, why not use a single product that is manufactured to near-identical specification in dozens of countries, sold by the same company and instantly recognisable to almost anyone on Earth?

The Big Mac fit the brief almost too well. It contains the same core inputs everywhere: beef, bread, cheese, lettuce, sauce, labour, rent, marketing and distribution. It is not a luxury item and not a commodity either – it is manufactured, priced and sold using local costs, wages and market conditions, but built to a global standard. That combination is exactly what economists need to test a theory.

Forty years on, the ‘joke’ has been the subject of dozens of academic papers, is taught in economics courses worldwide and is now published twice a year by The Economist as a serious, if self-consciously informal, dataset.

The theory underneath the bun

The Big Mac Index rests on purchasing power parity, or PPP – the idea that, in a perfectly efficient world, exchange rates should adjust so that an identical basket of goods costs the same amount everywhere once converted into a common currency. If it doesn’t, then in theory a currency is ‘mispriced’ relative to another.

Here’s the mechanic in practice. Take the price of a Big Mac in a given country’s own currency and divide it by the price of a Big Mac in the United States. That gives you an ‘implied exchange rate’ – the exchange rate at which burgers would cost exactly the same in both places. Compare that implied rate to the actual market exchange rate and the gap tells you whether the local currency looks overvalued or undervalued against the dollar, at least according to burgers.

A simplified example: if a Big Mac costs 500 yen in Japan and 5 dollars in the US, the implied exchange rate is 100 yen to the dollar. If the actual market exchange rate is instead 150 yen to the dollar, then the yen is buying more burger than the maths says it should – meaning the yen looks undervalued against the dollar by roughly a third.

Run that calculation across 50-plus countries, twice a year and you get a live, if unofficial, global temperature check on currency valuation.

Why it keeps showing up in serious rooms

The reason the index has outlived its origins as a bit of editorial fun is that, broadly, it works – with caveats. Big currency misalignments that the Big Mac Index flags do tend to show up in more sophisticated PPP models built from thousands of goods and services. Central banks and investors have cited it as a rough sanity check and it’s a staple in undergraduate economics courses precisely because it makes an abstract idea concrete in a single number anyone can picture.

The Economist itself has refined the tool over the years. Recognising that a burger costs more to make in a rich country simply because labour and rent are more expensive there – regardless of currency valuation – it introduced a GDP-adjusted version of the index. This adjustment strips out the part of the price difference that’s explained by income levels, plotting each country’s actual Big Mac price against what its GDP per person would predict. What’s left over is a cleaner signal of currency mispricing, separate from the simple fact that wages in Switzerland are higher than wages in Vietnam.

Where the model wobbles

The index has never claimed to be more than ‘lighthearted’ and its limitations are well documented and worth knowing before quoting it in a boardroom.

McDonald’s pricing isn’t purely a function of currency and input costs – it also reflects local competitive positioning, import tariffs on beef, real estate costs specific to prime retail locations, taxation and each market’s own pricing strategy. In some countries, eating atMcDonald’s is a mid-range treat; in others, it’s a premium, aspirational option, which pushes prices up independent of currency effects. The product itself isn’t always identical either – India’s Big Mac equivalent uses chicken rather than beef for cultural and religious reasons, McDonald’s isn’t present in a large number of countries at all and margins vary market to market based on how McDonald’s chooses to compete locally.

None of this invalidates the exercise. It just means the index is best read as a conversation starter and a rough directional signal, not a precision instrument.

The current picture

In The Economist’s most recent readings, the pattern that has held for years continues to hold: Switzerland consistently sits at the expensive end of the index, a function of high wages, high rents and a historically strong franc, while a cluster of Latin American and Asian economies – including Taiwan and Argentina in recent surveys – sit at the cheap end, reflecting weaker currencies and lower local costs. The United States itself sits somewhere in the upper-middle of the pack, which is precisely the benchmark the whole exercise is built around.

The eurozone is measured as a bloc rather than country by country, which means Malta’s own Big Mac price doesn’t get an individual line in The Economist’s official table – but the euro area’s reading still gives a useful proxy for where the region sits relative to the dollar, sterling and other major currencies that matter to a small, trade-exposed, tourism-heavy economy like ours.

Why this matters beyond the punchline

For a business audience, the value of the Big Mac Index isn’t really about burgers. It’s a reminder that exchange rates, inflation and the cost of living are not abstract line items – they show up in the price of the same product sitting on shelves from Zurich to Cape Town and the gaps between those prices tell a story about wages, currency strength and the true cost of doing business in a given market.

It’s also a genuinely useful case study in how to communicate complex economics well. Forty years after Pam Woodall’s original idea, the Big Mac Index remains one of the clearest examples of a piece of financial journalism that made a hard concept simple – without making it wrong.

Next time a Big Mac shows up on a menu somewhere on your travels, it’s worth checking the price. You might be looking at more than lunch.