What does a latte tell us about currencies? Very little, actually

Purchasing power parity is not the same as the Big Mac Index.

The Wall Street Journal sees what the Economist is having, and it likes it. The latter's Big Mac Index is famous for demonstrating the variation in prices for the same good around the world. Despite Big Macs being basically identical no matter where you are, the dollar price varies wildly, from $6.81 in Switzerland down to just $1.82 in India. It's so influential that it's widely thought that Argentina is exerting pressure on its branches of McDonalds to keep the price down so as to not provide evidence of the nation's tinkering with reported inflation.

So now the WSJ wants a piece of the action, and has created its Starbucks Latte Index. I mean, it doesn't call it that, but that's what they're thinking:

Click to embiggen.

But like the Economist, the WSJ draws the wrong inferences from the variation. They both have a habit of using the data to illustrate purchasing power parity, the idea that some currencies are under- or over-valued because a comparable basket of goods varies in price. So the WSJ's Ira Iosebashvili writes:

One way to determine how currencies stack up is purchasing-power parity, or PPP, which compares the amount of currency needed to buy the same item in different countries. A grande latte at Starbucks, for example, costs $4.30 in New York, but the equivalent of $9.83 using Norwegian krone in Oslo, and just $3.92 in Turkish lira in Istanbul.

Starbucks Lattes and Big Macs both have another unique feature, though, which renders them less useful for comparing the strength of a currency overall: they are both made up of highly fungible goods, produced in two of the most integrated supply chains in the world. McDonalds, for instance, doesn't need to buy artisanal wheat from an individual farm; it can just trade in "wheat" as a mass-produced, internationally-traded com oddity. The company has even invented a product to sell to take advantage of variations in the cost of pork, the McRib.

In fact, for Starbucks, that's even more true than it is for MacDonalds. While Maccy D's has made a big deal out of its promise to only use British beef in its British burgers, most of the countries Starbucks operates in in don't grow their own coffee. That has to be imported from South America or North Africa, and so a Starbucks in London will almost certainly be paying the same for its coffee as a branch in Oslo, despite the difference in retail price being over $6.

What the Starbucks and Big Mac indices actually show is the price of unskilled labour and retail space. Those are the parts of the companies' businesses which, no matter how hard they try, they can't erase national differences from. Operating in Oslo, land of high taxes, is always going to be expensive, no matter how strong or weak the krone is.

The Starbucks index even makes this clear, thanks to the fact that the WSJ has included three American cities. A latte in New York City costs more than one in Detroit, a difference that self-evidently can't be due to the currency variation.

But the really important news is that London is actually one of the cheapest cities in the world for a Starbucks latte. Still overpriced for what it is, though.

Alex Hern is a technology reporter for the Guardian. He was formerly staff writer at the New Statesman. You should follow Alex on Twitter.

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Can Philip Hammond save the Conservatives from public anger at their DUP deal?

The Chancellor has the wriggle room to get close to the DUP's spending increase – but emotion matters more than facts in politics.

The magic money tree exists, and it is growing in Northern Ireland. That’s the attack line that Labour will throw at Theresa May in the wake of her £1bn deal with the DUP to keep her party in office.

It’s worth noting that while £1bn is a big deal in terms of Northern Ireland’s budget – just a touch under £10bn in 2016/17 – as far as the total expenditure of the British government goes, it’s peanuts.

The British government spent £778bn last year – we’re talking about spending an amount of money in Northern Ireland over the course of two years that the NHS loses in pen theft over the course of one in England. To match the increase in relative terms, you’d be looking at a £35bn increase in spending.

But, of course, political arguments are about gut instinct rather than actual numbers. The perception that the streets of Antrim are being paved by gold while the public realm in England, Scotland and Wales falls into disrepair is a real danger to the Conservatives.

But the good news for them is that last year Philip Hammond tweaked his targets to give himself greater headroom in case of a Brexit shock. Now the Tories have experienced a shock of a different kind – a Corbyn shock. That shock was partly due to the Labour leader’s good campaign and May’s bad campaign, but it was also powered by anger at cuts to schools and anger among NHS workers at Jeremy Hunt’s stewardship of the NHS. Conservative MPs have already made it clear to May that the party must not go to the country again while defending cuts to school spending.

Hammond can get to slightly under that £35bn and still stick to his targets. That will mean that the DUP still get to rave about their higher-than-average increase, while avoiding another election in which cuts to schools are front-and-centre. But whether that deprives Labour of their “cuts for you, but not for them” attack line is another question entirely. 

Stephen Bush is special correspondent at the New Statesman. His daily briefing, Morning Call, provides a quick and essential guide to domestic and global politics.

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