The most important paragraph in the IMF World Economic Outlook

68 words of wonkishness.

The IMF's World Economic Outlook (pdf) – a 230-page tome detailing predictions on nearly every aspect of the world's economy collated by the international organisation – always gets attention for the calls it makes.

The October edition downgrades expected global growth for 2013 from 3.9 per cent to 3.6 per cent, and also cuts predictions for China (down to 8.2 per cent for 2013), the US (expected to grow by 2.1 per cent in 2013, down from 2.3 per cent in July's prediction) and the UK (now expected to grow by just 1.1 per cent next year, and to contract by 0.2 per cent this year).

But the predictions are not the most important passages in this edition of the Outlook. Those are found in a short box-out titled Are We Underestimating Short-Term Fiscal Multipliers?

The fisc§al multiplier is the effect government spending has on GDP. Money spent by the government doesn't disappear – it is respent, again and again. If a teacher gets a pay rise, their consumption is likely to rise in line with it; if all teachers get pay rises, that increase in consumption may be enough to affect the aggregate demand in the economy. In an economy which isn't being stretched to its limits – that is, one without full employment, or serious capital equipment shortages – that increase in aggregate demand will result in an increase in GDP.

The existence of the fiscal multiplier is a matter of fact, but the magnitude of it is contested. And that's where the IMF enters the scene, on page 42:

The main finding, based on data for 28 economies, is that the multipliers used in generating growth forecasts have been systematically too low since the start of the Great Recession, by 0.4 to 1.2, depending on the forecast source and the specifics of the estimation approach. Informal evidence suggests that the multipliers implicitly used to generate these forecasts are about 0.5. So actual multipliers may be higher, in the range of 0.9 to 1.7.

Emphasis mine. When deciding how much to spend, governments have been assuming that every pound they spend increases GDP by 50p – but it may increase it by as much as £1.70.

The reason this is so very important is that fiscal multiplier is usually appealed to not when deciding how much to spend, but how much to not spend. When governments are planning austerity packages, they have to be wary of the fact that large cuts to government spending will inevitably cause a decrease in output, and so they either have to be prepared to take that hit, or come up with a reason why slashing spending will cause an increase in output through some other mechanism.

That is easy enough to do if you are trying to account for a fiscal multiplier of 0.5: you can make the arguments, which Osborne and Cameron rehearsed repeatedly, that the public sector is crowding out the private; that the government spending which is being cut is particularly inefficient; or that the confidence fairies will reward your thriftiness with growth.

When there is the chance that the fiscal multiplier is three times that, austerity becomes much more likely to involve damaging drops in output.

There was once a time when the government pegged its credibility to that of the IMF – back when George Osborne was proud about Britain's credit ratings, and the international community was behind his plans. Those days are gone, and have been since Christine Lagarde made her own attack on austerity. But the economists at the treasury may be more inclined to listen to the wonkish findings of the World Outlook than the political interventions of the fund's leader. We can only hope they are prompted to re-do the sums.

The IMF headquarters. 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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A swimming pool and a bleeding toe put my medical competency in doubt

Doctors are used to contending with Google. Sometimes the search engine wins. 

The brutal heatwave affecting southern Europe this summer has become known among locals as “Lucifer”. Having just returned from Italy, I fully understand the nickname. An early excursion caused the beginnings of sunstroke, so we abandoned plans to explore the cultural heritage of the Amalfi region and strayed no further than five metres from the hotel pool for the rest of the week.

The children were delighted, particularly my 12-year-old stepdaughter, Gracie, who proceeded to spend hours at a time playing in the water. Towelling herself after one long session, she noticed something odd.

“What’s happened there?” she asked, holding her foot aloft in front of my face.

I inspected the proffered appendage: on the underside of her big toe was an oblong area of glistening red flesh that looked like a chunk of raw steak.

“Did you injure it?”

She shook her head. “It doesn’t hurt at all.”

I shrugged and said she must have grazed it. She wasn’t convinced, pointing out that she would remember if she had done that. She has great faith in plasters, though, and once it was dressed she forgot all about it. I dismissed it, too, assuming it was one of those things.

By the end of the next day, the pulp on the underside of all of her toes looked the same. As the doctor in the family, I felt under some pressure to come up with an explanation. I made up something about burns from the hot paving slabs around the pool. Gracie didn’t say as much, but her look suggested a dawning scepticism over my claims to hold a medical degree.

The next day, Gracie and her new-found holiday playmate, Eve, abruptly terminated a marathon piggy-in-the-middle session in the pool with Eve’s dad. “Our feet are bleeding,” they announced, somewhat incredulously. Sure enough, bright-red blood was flowing, apparently painlessly, from the bottoms of their big toes.

Doctors are used to contending with Google. Often, what patients discover on the internet causes them undue alarm, and our role is to provide context and reassurance. But not infrequently, people come across information that outstrips our knowledge. On my return from our room with fresh supplies of plasters, my wife looked up from her sun lounger with an air of quiet amusement.

“It’s called ‘pool toe’,” she said, handing me her iPhone. The page she had tracked down described the girls’ situation exactly: friction burns, most commonly seen in children, caused by repetitive hopping about on the abrasive floors of swimming pools. Doctors practising in hot countries must see it all the time. I doubt it presents often to British GPs.

I remained puzzled about the lack of pain. The injuries looked bad, but neither Gracie nor Eve was particularly bothered. Here the internet drew a blank, but I suspect it has to do with the “pruning” of our skin that we’re all familiar with after a soak in the bath. This only occurs over the pulps of our fingers and toes. It was once thought to be caused by water diffusing into skin cells, making them swell, but the truth is far more fascinating.

The wrinkling is an active process, triggered by immersion, in which the blood supply to the pulp regions is switched off, causing the skin there to shrink and pucker. This creates the biological equivalent of tyre treads on our fingers and toes and markedly improves our grip – of great evolutionary advantage when grasping slippery fish in a river, or if trying to maintain balance on slick wet rocks.

The flip side of this is much greater friction, leading to abrasion of the skin through repeated micro-trauma. And the lack of blood flow causes nerves to shut down, depriving us of the pain that would otherwise alert us to the ongoing tissue damage. An adaptation that helped our ancestors hunt in rivers proves considerably less use on a modern summer holiday.

I may not have seen much of the local heritage, but the trip to Italy taught me something new all the same. 

This article first appeared in the 17 August 2017 issue of the New Statesman, Trump goes nuclear