Comparing apples and oranges in data journalism: a case study

A must-read for any data journalist, aspiring or otherwise, is Simon Rogers’ post on The Guardian Datablog where he compares public and private sector pay.

This is a classic apples-and-oranges situation where politicians and government bodies are comparing two things that, really, are very different. Is a private school teacher really comparable to someone teaching in an unpopular school? What is the private sector equivalent of a director of public health or a social worker?

But if these issues are being discussed, journalists must try to shed some light, and Simon Rogers does a great job in unpicking the comparisons. From pay and hours worked, to qualifications and age (big differences in both), and gender and pay inequality (more women in the public sector, more lower- and higher-paid workers in the private sector), Rogers crunches all the numbers:

“[T]he proportion of low skill jobs in the private sector has increased, and the proportion of high skill jobs in the public sector increased to around 31% of all jobs by 2011, compared 26% of all private sector jobs.

“But, at the same time, people who are most highly qualified actually get paid worse in the public sector.

“… Public sector workers tend to be older … Average mean hourly earnings peak in the early 40s in both sectors. They decline slightly approaching retirement although the decline happens earlier in the private sector than in the public sector, possibly because the higher earners in the private sector are more likely to leave the labour market earlier.

“It also shows that if you’re older in the public sector, you get paid better than in the private sector.

“… [T]he bottom 5% of workers in the public sector earn less than £6.91 per hour, whereas in the private sector, 5% of workers earn less than £5.93 per hour.”

When you find yourself in an apples-and-oranges situation you can’t avoid, this is the way to do it. Any other examples?

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