See if you can work out the major statistical flaw in this Telegraph piece on marriage

It's not that hard…

It's bad stats Saturday, it seems. Before we start, see if you can work out for yourself what statistical stumble the Telegraph has made which renders this piece, headlined Almost no couples with children who stay unmarried stay together, study claims, entirely worthless. Go on, click through, we'll still be here.

Back? Hopefully you'll have been able to work out the main claim of the piece, which is that:

A study by the Marriage Foundation calculates that cohabiting couples who have children are more than twice as likely to split up as those who had tied the knot beforehand.

But of those who do not then go on to get married after having children, only a handful will still be together by the time the child is 16, it claims. [Emphasis mine]

It's a bold claim, and would certainly be a valuable fact for those who worry about the death of the "traditional" family to be able to point to. Unfortunately, it isn't true.

Further down the piece, we find the evidence behind the claim:

The report, which analyses figures from the Office for National Statistics, found that 93 per cent of couples whose relationships are still intact by the time their child is a teenager are married.

It calculated that out of a typical group of 100 16-year-olds, 45 of them would have experienced a family split, while 55 would still be living with both parents.

But only four of the 100 teenagers would have unmarried parents who are still together by the time they are 16. [Emphasis mine again]

In other words, of 100 sixteen-year-olds, only four have unmarried parents living together. That is, indeed, "only a handful" – but it is not a handful of "of those who do not go on to get married after having children". That figure is not given in the Telegraph report at all, and it's crucial. Without knowing what proportion of sixteen year olds were born to parents who were unmarried but living together, we can't know whether 4 per cent still living together is high, or low.

To find that out, we need to go to the original report, which claims that "out of the 47 per cent of children born to unmarried parents today… just 11 per cent will reach their 16th birthday with both parents intact and unmarried".

In other words, the survival rate of unmarried couples with children is over twice what the Telegraph implies; rather than 4 per cent, it is 11 per cent.

But there's something else as well. As the report says, "the rest will either marry or split up". In other words, a chunk of unmarried parents go on to marry before their child turns sixteen. That is also missed by the Telegraph's write up.

That is, where the paper writes that:

Only four of the 100 teenagers would have unmarried parents who are still together by the time they are 16.

It should actually read:

Only four of the 100 teenagers would have unmarried parents who are still together and still unmarried by the time they are 16.

And all of this stems from a report which is fundamentally based on assuming that patterns of marriage and cohabitation which were true for couples with children born in 1986 are still true for couples with children born in 2009. That's not something I'd stake money on; in case no-one noticed, we've had some pretty major changes to marriage recently.

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 tale of Battersea power station shows how affordable housing is lost

Initially, the developers promised 636 affordable homes. Now, they have reduced the number to 386. 

It’s the most predictable trick in the big book of property development. A developer signs an agreement with a local council promising to provide a barely acceptable level of barely affordable housing, then slashes these commitments at the first, second and third signs of trouble. It’s happened all over the country, from Hastings to Cumbria. But it happens most often in London, and most recently of all at Battersea power station, the Thames landmark and long-time London ruin which I wrote about in my 2016 book, Up In Smoke: The Failed Dreams of Battersea Power Station. For decades, the power station was one of London’s most popular buildings but now it represents some of the most depressing aspects of the capital’s attempts at regeneration. Almost in shame, the building itself has started to disappear from view behind a curtain of ugly gold-and-glass apartments aimed squarely at the international rich. The Battersea power station development is costing around £9bn. There will be around 4,200 flats, an office for Apple and a new Tube station. But only 386 of the new flats will be considered affordable

What makes the Battersea power station development worse is the developer’s argument for why there are so few affordable homes, which runs something like this. The bottom is falling out of the luxury homes market because too many are being built, which means developers can no longer afford to build the sort of homes that people actually want. It’s yet another sign of the failure of the housing market to provide what is most needed. But it also highlights the delusion of politicians who still seem to believe that property developers are going to provide the answers to one of the most pressing problems in politics.

A Malaysian consortium acquired the power station in 2012 and initially promised to build 517 affordable units, which then rose to 636. This was pretty meagre, but with four developers having already failed to develop the site, it was enough to satisfy Wandsworth council. By the time I wrote Up In Smoke, this had been reduced back to 565 units – around 15 per cent of the total number of new flats. Now the developers want to build only 386 affordable homes – around 9 per cent of the final residential offering, which includes expensive flats bought by the likes of Sting and Bear Grylls. 

The developers say this is because of escalating costs and the technical challenges of restoring the power station – but it’s also the case that the entire Nine Elms area between Battersea and Vauxhall is experiencing a glut of similar property, which is driving down prices. They want to focus instead on paying for the new Northern Line extension that joins the power station to Kennington. The slashing of affordable housing can be done without need for a new planning application or public consultation by using a “deed of variation”. It also means Mayor Sadiq Khan can’t do much more than write to Wandsworth urging the council to reject the new scheme. There’s little chance of that. Conservative Wandsworth has been committed to a developer-led solution to the power station for three decades and in that time has perfected the art of rolling over, despite several excruciating, and occasionally hilarious, disappointments.

The Battersea power station situation also highlights the sophistry developers will use to excuse any decision. When I interviewed Rob Tincknell, the developer’s chief executive, in 2014, he boasted it was the developer’s commitment to paying for the Northern Line extension (NLE) that was allowing the already limited amount of affordable housing to be built in the first place. Without the NLE, he insisted, they would never be able to build this number of affordable units. “The important point to note is that the NLE project allows the development density in the district of Nine Elms to nearly double,” he said. “Therefore, without the NLE the density at Battersea would be about half and even if there was a higher level of affordable, say 30 per cent, it would be a percentage of a lower figure and therefore the city wouldn’t get any more affordable than they do now.”

Now the argument is reversed. Because the developer has to pay for the transport infrastructure, they can’t afford to build as much affordable housing. Smart hey?

It’s not entirely hopeless. Wandsworth may yet reject the plan, while the developers say they hope to restore the missing 250 units at the end of the build.

But I wouldn’t hold your breath.

This is a version of a blog post which originally appeared here.

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