Wage stagnation in the US: more than meets the eye

If you can, always look below the surface of data.

Via the Economist journalist Daniel Knowles comes a good example of why its important to look below the surface of statistics. American economist Steve Landsburg addresses a commonly heard refrain – that the wage of the median worker has barely risen in the past thirty years – and shows that all is not as it seems.

Landsburg cites a book by economist Edward Conard (first chapter, containing what we're talking about, here), which itself cites the Census Bureau. I confess that, without a more specific citation, I can't find the exact data Conard uses, but have found similar enough data (pdf, table A-5) to confirm the overall thrust of the argument.

Conard shows that from 1980 to 2005, median income in the US rose just 3 per cent once inflation is taken into account, from $25,000 to $25,700. 2005 is pre-crash, as well, so this isn't a tale of the recession.

But when you break the data down by race and gender, a very different story appears:

  1980 Median 2005 Median Increase
All Workers 25,000 25,700 3%
White Men 30,700 35,200 15%
Nonwhite Men 19,300 22,300 16%
White Women 11,200 19,600 75%
Nonwhite Women 10,200 16,500 62%

For every single demographic group, there was a much bigger increase in the median wage than we see when the groups are combined. The reason for this is obvious when it's pointed out: demographic change in the US means that there are far more (low-salaried) women and people of colour working now than there were in 2005, which pushes the overall average down.

Landsburg illustrates it with a farmyard analogy:

Imagine a farmer with a few 100-pound goats and a bunch of 1000-pound cows. His median animal weighs 1000 pounds. A few years later, he’s acquired a whole lot more goats, all of which have grown to 200 pounds, while his cows have all grown to 2000. Now his median animal weighs 200 pounds.

A very silly person could point out to this farmer that his median animal seems to be a lot scrawnier these days. The farmer might well reply that both his goats and his cows seem to be doing just fine, at least relative to where they were.

This is almost an example of Simpson's Paradox, a well-known (to stats nerds) effect where the direction of a correlation disappears when that correlation is disaggregated. I was taught it with an example involving racial discrepancies in application of the death penalty:

Sixty per cent of white murderers are executed for their crimes, and fifty per cent of black murderers. Are black people discriminated against in the application of the death penalty?

Now suppose that we break down the murder victims by race as well. We find the common pattern that people tend to attack victims of their own race:

Number of murders where death penalty is applied

White Murderer Black Murderer
White Victim 50/70=71% 25/30=83%
Black Victim 10/30=33% 25/70=36%

What about now? Does it begin to look like black people are discriminated against? In this example, black people are more likely to be executed for the murder of black or white victims; but because the murder of black victims isn't taken as seriously by the courts, the fact that murderers predominantly attack people of their race makes it look like black people are less likely to be executed than white people.

The median income example isn't quite a case of Simpson's Paradox, because there is still a positive increase in wage whether or not the statistics are disaggregated. But it's still an example of a time when it is best to dig beneath the surface.

But there is more to be said on the story of wage stagnation. Because a second claim normally accompanies the belief that US wages have stagnated, and that is that there has been a "decoupling" of wages. Due to rising inequality, the median household wage hasn't risen as fast as the mean wage:

If we've seen that the median wage grows faster when disaggregated, then the solid red line is likely to take a steeper ascent. But what happens to the dashed red line when disaggregated?

Sadly, I cannot find the data required to answer the question. If anyone knows where to look, tell me, and maybe we can put the issue to rest.

An immigrant worker protests in Orlando, Florida. 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: Jeremy Corbyn prompts Tory outrage as he blames Grenfell Tower fire on austerity

To Conservative cries of "shame on you!", the Labour leader warned that "we all pay a price in public safety" for spending cuts.

A fortnight after the Grenfell Tower fire erupted, the tragedy continues to cast a shadow over British politics. Rather than probing Theresa May on the DUP deal, Jeremy Corbyn asked a series of forensic questions on the incident, in which at least 79 people are confirmed to have died.

In the first PMQs of the new parliament, May revealed that the number of buildings that had failed fire safety tests had risen to 120 (a 100 per cent failure rate) and that the cladding used on Grenfell Tower was "non-compliant" with building regulations (Corbyn had asked whether it was "legal").

After several factual questions, the Labour leader rose to his political argument. To cries of "shame on you!" from Tory MPs, he warned that local authority cuts of 40 per cent meant "we all pay a price in public safety". Corbyn added: “What the tragedy of Grenfell Tower has exposed is the disastrous effects of austerity. The disregard for working-class communities, the terrible consequences of deregulation and cutting corners." Corbyn noted that 11,000 firefighters had been cut and that the public sector pay cap (which Labour has tabled a Queen's Speech amendment against) was hindering recruitment. "This disaster must be a wake-up call," he concluded.

But May, who fared better than many expected, had a ready retort. "The cladding of tower blocks did not start under this government, it did not start under the previous coalition governments, the cladding of tower blocks began under the Blair government," she said. “In 2005 it was a Labour government that introduced the regulatory reform fire safety order which changed the requirements to inspect a building on fire safety from the local fire authority to a 'responsible person'." In this regard, however, Corbyn's lack of frontbench experience is a virtue – no action by the last Labour government can be pinned on him. 

Whether or not the Conservatives accept the link between Grenfell and austerity, their reluctance to defend continued cuts shows an awareness of how politically vulnerable they have become (No10 has announced that the public sector pay cap is under review).

Though Tory MP Philip Davies accused May of having an "aversion" to policies "that might be popular with the public" (he demanded the abolition of the 0.7 per cent foreign aid target), there was little dissent from the backbenches – reflecting the new consensus that the Prime Minister is safe (in the absence of an attractive alternative).

And May, whose jokes sometimes fall painfully flat, was able to accuse Corbyn of saying "one thing to the many and another thing to the few" in reference to his alleged Trident comments to Glastonbury festival founder Michael Eavis. But the Labour leader, no longer looking fearfully over his shoulder, displayed his increased authority today. Though the Conservatives may jeer him, the lingering fear in Tory minds is that they and the country are on divergent paths. 

George Eaton is political editor of the New Statesman.

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