Monday 4 May 2020

The problem of averages

Averages and aggregated data, in general, are a useful way of comparing and presenting data, but they can often hide an important level of detail which makes them dangerous as a basis for setting policy, particularly when they end up being interpreted as though all the individual items are at the ‘average’ level. One example which immediately springs to mind is the regular comparison between average spend per pupil in Welsh schools and average spend per pupil in English schools, a comparison which reflects poorly on Welsh schools, usually indicating a ‘deficit’ of around £600 per pupil per year. Now there are a variety of reasons why there might be a gap, but what such ‘averages’ hide is that there are some Welsh schools which receive more than the English average and some English schools which receive less than the Welsh average. More importantly, whilst the gap between the English and Welsh averages can be ‘solved’ by simply giving £600 per pupil per year extra to all schools in Wales (as some politicians have called for), that won’t address the differences between funding levels when comparing schools within Wales (or within England). It’s addressing the data rather than the problem, but numeracy does not seem to be a particularly strong trait amongst politicians.
We’re seeing another example of this at the moment in relation to the pandemic, with claims by English government ministers that the UK is now ‘past the peak’. It’s one of those statements which is ‘true’ but which isn’t the whole truth. The fact that the UK at an aggregate level is now seeing reducing numbers doesn’t mean that all parts of the UK are seeing reducing numbers, either geographically or in terms of sectors (such as care homes), and taking UK-wide decisions on the easing of the lockdown on the basis of an aggregated data set means that lockdown could be eased at a time which is still too early for any areas or sectors which have yet to pass the peak. It could exacerbate the rate of infection in those areas as a result. Yet that is exactly what the PM’s rhetoric suggests he wants to do. The annoyance with which more cautious statements from the First Ministers of Wales and Scotland are greeted is another indication of the way in which the overall situation is being wrongly interpreted. The First Ministers are right to make it clear that they reserve the right to act differently if the situation in their respective countries is different; I hope that they will also understand that the situation might vary within their countries as well as between them. The same distinction also applies in England – just because London’s figures are falling fairly consistently does not mean that all parts of England are past the peak yet either; they just don’t have First Ministers to stand up for their interests.
When the rate of transmission varies across a country it inevitably causes problems in taking decisions – should we wait to ease the lockdown until all parts are on a clear downward trend, accepting that that will be later than necessary for some; should we ease the lockdown as soon as the overall picture improves sufficiently, accepting that it will be too early for some; or should we vary the decision according to circumstances in different areas? None of these are ideal – all bring real problems, both economically and socially, to say nothing of the impact in terms of sickness and death. The PM’s instinct seems to be to use the aggregate figures as his guide and apply policy across the board; I just wish I could be confident that he and his government were doing that on the basis of an understanding of the compromises involved rather than simply an inability to understand what averages and aggregates are telling us.

4 comments:

Jonathan said...

"should we ease the lockdown as soon as the overall picture improves sufficiently, accepting that it will be too early for some; or should we vary the decision according to circumstances in different areas?" Do it by areas. The US illustrates why. Of the 50 States 35 are now actively working on opening up. My wife is from South Dakota which never felt the need to close, being all prairie and Black Hills. But home is now N.Carolina where the decision is on a knife edge. Moderate State, at least 2 big urban centres. Any decision to re-open NC will have consequences at the ballot box when they come to re-elect the Governor (or not). NC has 100 Counties, so one way forward may be to open Carteret County (beach) and keep Wake County (urban) closed for longer. The point is that the system allows for flexibility. Important when circumstances vary but (key) so do attitudes. The bolder souls can open. The more timid ones can stay closed and watch how bold works out. Wales has the administrative structures (Devolution, Counties) to experiment but it still comes down to attitude. For heaven's sake Wales could open Garden Centres and DIY shops even if England does not. But treating the virus like the Blitz (singing "We'll meet again" on Friday?) means no. Welsh Labour could score big time by going it alone. But they won't, will they.

dafis said...

Given that various regions are "enjoying" different levels of the virus, some past their peak while others may still be escalating,there may be a case for easing the lockdown in a similarly differentiated pattern. The weakness arises when we take into account the amount of travel between regions. For instance we don't want a repeat or any increase in the rush of 2nd homers, caravaners and BnB visitors just because lockdown is eased in say Birmingham but not in Gwynedd.

Would Drakeford &Co have the backbone to put up the no entry signs at County borders or would they defer tamely to the "needs" of our tedious neighbours?

John Dixon said...

"The weakness arises when we take into account the amount of travel between regions." Precisely. Like Jonathan, I favour doing it by areas, but recognising that the differentiating factor is the progress of the virus rather than convenient administrative boundaries between jurisdictions. None of the options is problem-free, and that is nothing at all to do with boundaries between the nations of the UK. I do not believe, however, that centralist English nationalists are capable of adopting the necessary mindset. Whether the Welsh government has the courage to insist has yet to be seen.

Jonathan said...

Here's the oddity about borders. The English think shock/horror or mock you if you say Wales could have borders. "Ho, Ho! Customs posts along Offa's Dyke? Where? Buttington Cross? Monmouth? The very idea...!" Or, as Dafis says, - "We do not divide our United Kingdom" etc. Well I don't like borders either, being a Schengen sort of person. But. When I flew from Kairdiff to Edinburgh a while ago I had to show my passport. And just the other day, over Easter, the Welsh police WERE patrolling Wales' borders. Or at least stopping travellers somewhere, close to their boundaries, which is the same thing if you're the Dyfed-Powys Police or Heddlu'r Gogledd. But not strictly the act of a Welsh Government, its true. As I've said before, its the right to have a border that counts for a country/State. Wales need not apologise for declaring its own border. Doesn't mean you need a hut, rising barrier and "Papers please!" 24/7. Just in certain circumstances........