The inadequacy of averages in setting targets

ONS tweet - Londoners well-being has improved but still remains below the UK average  #wellbeing
Tweet from the Office for National Statistics on the well-being of Londoners, 24 September 2014

Yesterday, 24 September 2014, the Office for National Statistics (ONS) released its latest findings on the UK population’s personal well-being, popularly known as the ‘Happiness Index’.

They tweeted quite a bit about the results. The tweet that London’s well-being was lower than the UK average caught my eye. It reminded me of the problems that policy makers face if they interpret being below average as being inadequate.

But first, what has ONS measured?

Well, the figures come from data collected between April 2013 and March 2014 for the Annual Population Survey. Responses are from 165,000 people, which is an impressively large number.

ONS asked four questions:

  • Overall, how satisfied are you with your life nowadays?
  • Overall, to what extent do you feel the things you do in your life are worthwhile?
  • Overall, how happy did you feel yesterday?
  • Overall, how anxious did you feel yesterday?

All are answered using a 0 to 10 scale where 0 is ‘not at all’ and 10 is ‘completely’.

The breakdown by English region shows that, compared to the UK average, only the London region has figures that are ‘worse’ (lower for the first three questions, higher for the fourth). This is probably why ONS picked out London to tweet about.

The figures were:

London (mean) UK (mean) average Difference
Life satisfaction 7.37 7.51 -0.14
Worthwhile 7.64 7.74 -0.1
Happiness 7.32 7.38 -0.06
Anxiety 3.18 2.32 0.86

Although small, the differences are statistically significant according to ONS. Surely something must be done?

Quite possibly. But quite possibly not.

The thing about averages is that it’s impossible for everything to be above average.

What we need to know is if London’s scores aren’t meeting some acceptable threshold value. If not then action is needed. What is an acceptable score? Well, that is for the policy makers to decide. But if they base it on an average then they pretty much set themselves up for failure somewhere.

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