The risks of imprecision

When being half-right can be worse than being wrong.

Chris Dillow has a nice post up, "in praise of imprecision". He argues that, in far too many situations, we argue over tiny differences in estimates when the overall answer is basically known. What's GDP growth for last year? It's basically flat. Yet for all the arguments, you would think that the difference between -0.3 and -0.1 per cent – or even between -0.1 and 0.1 – was the difference between life and death.

He illustrates this with a few neat little guesstimates. For instance:

How much does welfare scrounging cost the economy? Guesstimate the number of scroungers. Guesstimate the value-added they'd contribute if they were working. Express as a proportion of GDP. For plausible values, it's a small number.

Or:

What impact will the small uprating in the minimum wage have on jobs? The adult rate will rise by 1.9%. Economists forecast inflation this year of 2.5%, so this is roughly a 0.6% real fall. Let's call the price-elasticity of demand for labour 1.5. The Low Pay Commission estimates (pdf) that 5.3% of jobs are around minimum wage ones. Multiply these three numbers together and we get 0.048%. Multiply by the number of jobs in the economy (29.73m) and we have roughly 14,000.That's roughly one-eleventh of the sampling variability of employment figures.

It's worth pointing out that the same idea has been applied pretty consistently to the claim that families with three generations of worklessness are a public policy problem. We don't know how many there are – and nor does the government, we now know – but study after study has suggested that the number is tiny.

There are only 15,000 households with two generations which have never worked, and a third of them are because the younger generation left full time education within the last year. On top of that, less than 1 per cent of young people have never worked by the age of 29, so the younger generation is normally the one most likely to pull a family out of worklessness. Whatever the number is, in other words, it's really, really small.

But it's important to note the downside to imprecision. The way common knowledge is disproved is rarely through wholesale upheaval. Instead, it's a gradual process of refinement: new estimates are put out, slightly lower than the old ones; then lower estimates still; and they get steadily lower, until suddenly you realise that the conventional wisdom was wrong.

It's a lot harder to turn an estimate of "recession" into an estimate of "growth" through gradual refinement than it is to turn an estimate of "-0.3 per cent" into one of "0.5 per cent". So there's more of a danger that we'll be stuck with half-truths.

But with that danger in mind, the absence of accepted imprecision is still keenly felt in Whitehall. Too frequently, "no statistics" is used to imply "we have no idea of the magnitude of this problem" – but that's not true. We actually know quite a lot, albeit imprecisely. The trick is acting on it.

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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The dog at the end of the lead may be small, but in fact what I’m walking is a hound of love

There is a new, hairy face in the Hovel.

There is a new, hairy face in the Hovel. I seem to have become a temporary co-owner of an enthusiastic Chorkie. A Chorkie, in case you’re not quite up to speed with your canine crossbreeds, is a mixture of a chihuahua and a Yorkshire Terrier, and while my friend K— busies herself elsewhere I am looking after this hound.

This falls squarely into the category of Things I Never Thought I’d Do. I’m a cat person, taking my cue from their idleness, cruelty and beauty. Dogs, with their loyalty, their enthusiasm and their barking, are all a little too much for me, even after the first drink of the day. But the dog is here, and I am in loco parentis, and it is up to me to make sure that she is looked after and entertained, and that there is no repetition of the unfortunate accident that occurred outside my housemate’s room, and which needed several tissues and a little poo baggie to make good.

As it is, the dog thinks I am the bee’s knees. To give you an idea of how beeskneesian it finds me, it is licking my feet as I write. “All right,” I feel like saying to her, “you don’t have to go that far.”

But it’s quite nice to be worshipped like this, I have decided. She has also fallen in love with the Hovel, and literally writhes with delight at the stinky cushions on the sofa. Named after Trude Fleischmann, the lesbian erotic photographer of the Twenties, Thirties and Forties, she has decided, with admirable open-mindedness, that I am the Leader of the Pack. When I take the lead, K— gets a little vexed.

“She’s walking on a loose lead, with you,” K— says. “She never does that when I’m walking her.” I don’t even know what that means, until I have a think and work it out.

“She’s also walking to heel with you,” K— adds, and once again I have to join a couple of mental dots before the mists part. It would appear that when it comes to dogs, I have a natural competence and authority, qualities I had never, not even in my most deranged flights of self-love, considered myself to possess in any measurable quantity at all.

And golly, does having a dog change the relationship the British urban flâneur has with the rest of society. The British, especially those living south of Watford, and above all those in London, do not recognise other people’s existence unless they want to buy something off them or stop them standing on the left of the sodding escalator, you idiot. This all changes when you have a dog with you. You are now fair game for any dog-fancier to come up to you and ask the most personal questions about the dog’s history and genealogy. They don’t even have to have a dog of their own; but if you do, you are obliged by law to stop and exchange dog facts.

My knowledge of dog facts is scant, extending not much further beyond them having a leg at each corner and chasing squirrels, so I leave the talking to K—, who, being a friendly sort who could probably talk dog all day long if pressed, is quite happy to do that. I look meanwhile in a kind of blank wonder at whichever brand of dog we’ve just encountered, and marvel not only at the incredible diversity of dog that abounds in the world, but at a realisation that had hitherto escaped me: almost half of London seems to have one.

And here’s the really interesting thing. When I have the leash, the city looks at me another way. And, specifically, the young women of the city. Having reached the age when one ceases to be visible to any member of the opposite sex under 30, I find, all of a sudden, that I exist again. Women of improbable beauty look at Trude, who looks far more Yorkie than chihuahua, apart from when she does that thing with the ears, and then look at me, and smile unguardedly and unironically, signalling to me that they have decided I am a Good Thing and would, were their schedules not preventing them, like to chat and get to know me and the dog a bit better.

I wonder at first if I am imagining this. I mention it to K—.

“Oh yes,” she says, “it’s a thing. My friend P-J regularly borrows her when he wants to get laid. He reckons he’s had about 12 shags thanks to her in the last six months. The problems only arise when they come back again and notice the dog isn’t there.”

I do the maths. Twelve in six months! That’s one a fortnight. An idea begins to form in my mind. I suppose you don’t have to be a rocket scientist to work out what it is. But no. I couldn’t. Could I?

Nicholas Lezard is a literary critic for the Guardian and also writes for the Independent. He writes the Down and Out in London column for the New Statesman.

This article first appeared in the 28 April 2016 issue of the New Statesman, The new fascism