small caged mammal confessions

Unlock the Editor’s Digest for free

There was, briefly, a risk that FT Alphaville’s recent Art of the Chart show would occur without any small caged mammal representation.

But the arc of the mammalian universe bends towards content, and so — thanks largely to the Herculean efforts of MainFT graphics éminence Alan Smith — this graphic exists (zoomable image here):

Long-term fans of our scm coverage may recognise this is basically a fancier, mappier version of the extensive chart set we made last summer. The idea was to show the weird behaviour of prices recorded for a “small caged mammal”, one of the items the Office for National Statistics observes to track inflation, at individual shops, by showing every shop as its own line chart.

And, yeah, those lines are often weird — which suggests to us that despite some guidance (more on that here)…

…small caged mammal remains a slightly nebulous item type.

However, we have a confession. In the process of preparing the data for Sir Alan, we found our system of coding the price series of individual shops contained two material errors.

blunder 1

The first one went like this: in the ONS’s price quotes tables (aka the best data sets ever), each price comes with metadata including the region in which the vendor is based, and a unique shop code. The ONS’s guidance on how to use this data can be found here (nb that’s a direct download link).

When we made our shop-by-shop series, we gave each a name that combined its region (eg London) with its shop code (eg 023), leaving us with a set of shop like, uh, “London-023”.

We thought this sorted all our problems…

…but in our arrogance and conceit, we failed to realise that shops with the same code could also be distinguished by whether they were an independent (with 10 shops or fewer) or a multiple (with more than 10 shops). So, for instance, there could be London-023-Independent AND London-023-Multiple.

In retrospect, the fact that we’d made an error was obvious, because some of the charts showed prices that went beyond the actual highest price, a result of us summing two prices when an independent and multiple had the same region and code. It truly sucks to suck.

As far as we can tell, region, shop type and shop code are the three categories that determine a unique shop, so we think we’ve now completely fixed the issue — but how many shops did this effect?

By our count… three, which is to say we accidentally merged six shops into three: London-035, Scotland-016 and Scotland-029.

Unfortunately, though perhaps expectedly, all three are among those we then called out for having unusual price movements…

…and narrativised thusly:

— London-035: [2020–2024] Davide had been on the ONS small caged mammal beat for a while now, and still wasn’t really sure what he was looking for.
— Scotland-016: [2020–2024] Drawing a six-sided dice from her coat pocket, Anita prepared to determine what kind of mammal she’d look at this month.
— Scotland-029: [Late 2019] “We gotta switch things up. The sub-£45 mammal market — that’s where the money is.”

Fixing our error — and therefore splitting these up appropriately — the charts instead look like this:

It certainly makes London-035 look a bit more reasonable (although it still appears a marked chinchilla shift occurred at 035-M after the UK’s initial Covid-19 lockdowns), and Scotland-029 not longer has the severe price drop at the start. Scotland-016-M is still pretty weird.

blunder 2

Blunder 1 is stupid, but we’d dare to suggest understandable. Blunder 2 is a little harder to excuse.

Y’all, we erased Northern Ireland.

As mentioned, all these prices come with metadata including region. The regions are coded 1 to 13, where 1 is “catalogue collections” (we’re not sure how literally to interpret this), and 2 to 13 are regions of the UK. Northern Ireland is number 13 in this collection, Scotland is 12.

And, while converting the data to make our silly little name strings, it seems we converted both 12s and 13s into “Scotland”, dragging 10 Northern Irish shops into the Caledonian batch.

We would like to take this opportunity to apologise to anyone who has ever been associated in any way with Northern Ireland. Liam Neeson, Nadine Coyle, Kadhim Shubber, the Derry Girls… we’re sorry.

As far as we can tell, this will only have affected the actual line for one previously-presented shop, “Scotland-045” — which did exhibit a slightly odd uptick, and should in fact have been one NI shop and one Scottish one:

small caged mammal redemption?

Thankfully, these errors all got caught BEFORE we embarrassed ourselves by sending bad data to Alan and the graphics gang. The chart show map pictured above included the correct (we think!) series, and actually reflected all the members of the United Kingdom. Wahey.

But Northern Ireland deserves the representation we cruelly denied it last summer, so here’s all the little charts again, fixed and running up to the end of 2024: