Very imaginative statistics

Thank you to South West Water (SWW) for the inspiration for this blog post.  Like many homes in the UK, we have a water meter and pay for our water usage by the cubic metre.  We pay quarterly, with a reading by SWW every six months and an estimated reading every three months.  Over the past year (October - September) the annual usage was about 55 cubic metres; the meter is read to whole numbers of cubic metres.  However, when I went to pay the latest bill, I was startled to see the graph below.  It claims to show our average daily usage of water month by month for the last two years.  How on earth can that be the case?

Let us leave aside the presence of 13 dots on the solid line, one of which claims to show the average consumption for the month (October 2024) which is only just starting.  Let us also lay aside the x-axis which is labelled with month and year and then there is a dotted line for a different year.  Let us lay aside the suppressed zero on the y-axis.  And what does the line between dots really mean?

No, think about how the company claims to know about daily consumption when the readings are taken at such large intervals.  How is it done? 

 Answer --- with great imagination.  They use averages and scaling.   Based on their supply data, they can assign fractions, f(1), f(2), ... f(12) to each month's demand for customers in my area of Devon.  then they take my 55 cubic metres, scale it by those fractions and scale it by the length of the month and ... HEY PRESTO! ... we have this graph.  I ran it through a spreadsheet and reverse engineered it to confirm that those dots do scale up to 55. 

So, this is imaginative.  Also wrong. Also pointless --- can it affect my behaviour?  As I have remarked elsewhere, numerical information should be communicated clearly and accurately.  Anything else is smoke and mirrors.