Photo by Xosema (Own work) [GFDL or CC BY-SA 4.0-3.0-2.5-2.0-1.0], via Wikimedia Commons
“Cauliflower prices,” I thought to myself when I opened the data set. “Those damn Banters and their cauliflower bases.”
The data in front of me contained monthly market reports on vegetable prices. I was looking at the data holistically, but an interesting trend caught my eye. Cauliflower prices were up, big time.
It’s a story alright, but writing a story about one of the most boring vegetables that doesn’t make readers slip gently into a collective coma was not easy.
The Banting diet, punted by Profesor Tim Noakes has divided households since he backed it in his book The Real Meal Revolution, in 2014.
The merits of the diet remain controversial, but as it turned out, the allegation that Banting has pushed up cauliflower prices – at least at the wholesale level – is unfounded.
For years, I had longed for something in the numbers that would put the Banters in their places. Now I had the data, but data doesn’t lie, and neither could I went I wrote the story. Unfortunately, the Banters are off the hook.
The cauliflower prices and sales volumes were notes in the market reports, so it took some time to extract them and put them into my own data base.
At first I could not see any pattern but then I did two things:
First, I worked out the month-on-month and then the year-on-year percentage difference for prices and tons sold. I still did not see anything of significance.
But then I took an extra step. I decided to conditionally format the percentage differences in Excel for the year-on-year data by giving them different colours to show changes in prices and volumes.
Voila! The cause and effect became obvious. Every time there was a year-on-year spike in supply, there was a corresponding drop in prices. The inverse was true when supply fell.
I put the data in a graph (see below) which showed a correlation between supply and demand that could easily come out of an economics textbook.
The graph not only shows an efficient market at work, it also exonerates Banters. For now.
