The Billy bookcase is perhaps the archetypal Ikea product.

It was dreamed up in 1978 by an Ikea designer called Gillis Lundgren who sketched it on the back of a napkin, worried that he would forget it.

Now there are 60-odd million in the world, nearly one for every 100 people – not bad for a humble bookcase.

In fact, so ubiquitous are they, Bloomberg uses them to compare purchasing power across the world.

According to the Bloomberg Billy Bookcase Index – yes, that’s a thing – they cost most in Egypt, just over $100 (£79), whereas in Slovakia you can get them for less than $40 (£31).

Every three seconds, another Billy bookcase rolls off the production line of the Gyllensvaans Mobler factory in Kattilstorp, a tiny village in southern Sweden.

Read the whole article at bbc.com