Thames Water is the UK’s largest water utility. As their website proudly boasts, they “take care of water for 16 million people”. That’s around 24% of the UK population. This concerns me, but not only for the reason you might expect…

The company has made the headlines in recent months for their tawdry performance when it comes to the discharge of untreated sewage into the water catchments for which they have responsibility. My concern, however, is with a paper-based form of pollution.

The bill they sent me this week includes the chart pictured below. You will see that Thames Water have endeavoured to make the consumption of their product understandable by expressing it in “cups of tea per day” (COTPD). Whether this rather quaint currency resonates with their customers I don’t know, but the chart is a disgrace.

The complete absence of any kind of scale makes it worse than meaningless. The bar for the period in which there was no water consumed at all is only marginally lower than that for the preceding period when the consumption rate was 146 COTPD.

Equally, the bar for the 146 COTPD period is 11.5mm high, whilst the bar for the 511 COTPD period is 21mm high (oh yes, I’ve measured!). This implies the COTPD rate in the latter period was around twice that in the former period, when it was actually 3.5x greater.

Why on earth should I care, you might ask? Aren’t I just being a numerical pedant?

I would seek to disagree. As we know, this nonsense chart or its equivalent is being sent to some 16 million people.

According to the OECD, England ranks 21st out of 38 member countries for numeracy skills (source: OECD www.compareyourcountry.org).

In a recent report published by the charity National Numeracy they point out that, “49% of the working-age population of England have the numeracy level that we expect of primary school children. The total cost to the UK economy…has been put at £20 billion a year”.

Furthermore, in a survey commissioned by the same charity last year, KPMG found that 35% of adults say that “doing maths” makes them feel anxious, while an alarming 29% “say they actively try to avoid anything to do with numbers”.

Not only does this have worrying implications for the country’s economic prospects, it should also give grave cause for concern about how well-equipped people are to manage their personal finances.

To take one example, as Martin Lewis succinctly points our on his website, “For around a quarter of a century, we’ve educated our youth into debt when they go to university, but never about debt.”

That steps are now being taken to introduce personal finance into the school curriculum is to be welcomed, but more needs to be done.

Charts such as the one published by Thames Water can only serve to confuse and further undermine confidence. They are graphic effluent and should be stopped.