Is This Why Egg Sales Are Up (in USA)

This came up in this morning's edition of More Or Less, the BBC Radio Four statistics-magazine that examines the claims made by politicians, journalists, advertisers and campaigners, often finding them deeply flawed.


President Trump had reckoned the price of eggs has fallen by 400%.


That means, by his simple example price, if a carton of eggs had cost $10, the shop now gives you $30 to take it away!

I must admit I had to use my calculator to understand the explanation, but it goes like this:


Any reduction of n% means the Sale price = Original Price - [n% of Original]

So if we start at $10, 50% reduction clearly halves the price: 10 - (10 X 50/100) = $5.

90% reduction gives 10 - (10 X 90/100) = 10 - 9 = $1.

You might expect 100% off to make the eggs free. Indeed it does: 10 - (10 X 100/100) = $0

So Mr.Trump's claim comes to

10 - (10 X 400/100) = 10 - 40 = $-30 (i.e. minus-thirty Dollars) so free eggs plus $30 from the unfortunate shopkeeper!

.....

Tim Harford, the economist who presents the programme, did explain the price of eggs generally in America has lowered thanks to greater availability by recovery from an avian-flu epidemic, and imports. Not by 400% though! Nearer $40% (So down to $6 by his example cost.)
....

Politicians be politicians.....

Oh, don't worry our home-grown ones in Britain are not always much more numerate; and for anything technical most are hopelessly naive. (Think of Boris Johnson's ideas to create an artificial island in the Thames Estuary for an airport, and allegedly at least, a tunnel connecting Ireland and Scotland at their closest points. Or HS2, by all parties.)

As simple numbers game though, I recall one Opposition MP becoming so excited at the Government having reversed some decision, she exclaimed,