Is Excel the most dangerous piece of software in the world?

Microsoft's calculator is partially to blame for JPMorgan losing $9bn, and a lot more besides.

Is Excel the most dangerous piece of software in the world? Baseline Scenario's James Kwak reports on a little-mentioned aspect of the notorious "London Whale" debacle at JPMorgan, where Bruno Iksil headed a proprietary trading team which made losses of up to $9bn.

It turns out, Kwak writes, that Excel was partly to blame:

To summarize: JPMorgan’s Chief Investment Office needed a new value-at-risk (VaR) model for the synthetic credit portfolio (the one that blew up)… The new model “operated through a series of Excel spreadsheets, which had to be completed manually, by a process of copying and pasting data from one spreadsheet to another”… After the London Whale trade blew up, the Model Review Group discovered that the model had not been automated and found several other errors. Most spectacularly,

“After subtracting the old rate from the new rate, the spreadsheet divided by their sum instead of their average, as the modeler had intended. This error likely had the effect of muting volatility by a factor of two and of lowering the VaR…”

Kwak wonders if the very ease of use that Excel offers — allowing people with no programming experience to knock together what are, in effect, relatively advanced applets — also makes it dangerous to use in most sensitive situations. There's no debug, no audit trail, and no way to test why a spreadsheet returns the value it does. Similarly, training for Excel, where it exists, tends to ignore the importance of elegant and well-designed code, leading to legacy spreadsheets being used with internal workings which are opaque to all but their original creator, who may have left the company 20 years earlier.

The problem is, though, that Excel is the worst way to run a company's software other than all the other ways. The fact that it's capable of being programmed by the people who will end up using it means that it might enable hacked-together code, but it also prevents exactly the sort of corporate bloat which leads to people circumventing their company's software in the first place.

Bill Gates threatens the world with Microsoft Office in 2003. Photograph: Getty Images

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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PMQs review: Theresa May shows again that Brexit means hard Brexit

The Prime Minister's promise of "an end to free movement" is incompatible with single market membership. 

Theresa May, it is commonly said, has told us nothing about Brexit. At today's PMQs, Jeremy Corbyn ran with this line, demanding that May offer "some clarity". In response, as she has before, May stated what has become her defining aim: "an end to free movement". This vow makes a "hard Brexit" (or "chaotic Brexit" as Corbyn called it) all but inevitable. The EU regards the "four freedoms" (goods, capital, services and people) as indivisible and will not grant the UK an exemption. The risk of empowering eurosceptics elsewhere is too great. Only at the cost of leaving the single market will the UK regain control of immigration.

May sought to open up a dividing line by declaring that "the Labour Party wants to continue with free movement" (it has refused to rule out its continuation). "I want to deliver on the will of the British people, he is trying to frustrate the British people," she said. The problem is determining what the people's will is. Though polls show voters want control of free movement, they also show they want to maintain single market membership. It is not only Boris Johnson who is pro-having cake and pro-eating it. 

Corbyn later revealed that he had been "consulting the great philosophers" as to the meaning of Brexit (a possible explanation for the non-mention of Heathrow, Zac Goldsmith's resignation and May's Goldman Sachs speech). "All I can come up with is Baldrick, who says our cunning plan is to have no plan," he quipped. Without missing a beat, May replied: "I'm interested that [he] chose Baldrick, of course the actor playing Baldrick was a member of the Labour Party, as I recall." (Tony Robinson, a Corbyn critic ("crap leader"), later tweeted that he still is one). "We're going to deliver the best possible deal in goods and services and we're going to deliver an end to free movement," May continued. The problem for her is that the latter aim means that the "best possible deal" may be a long way from the best. 

George Eaton is political editor of the New Statesman.