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This is the short edition of More or Less, first broadcast on the BBC World Service.

Hello and welcome to More or Less on the BBC World Service.

I'm Tim Harford.

This week the story of how two economists who disagree with each other

have been jointly awarded the Nobel Memorial Prize for Economics.

The story begins at the start of the 20th century in Paris.

Louis Bachelier, aspiring physicist, lives a life filled with misfortune.

Both parents die, leaving him holding his baby brother, drafted into the army,

misses the window to study at the Grande Col.

Studies Physics at night school and trades bonds by day to pay the bills.

It reduces one of Einstein's famous results before Einstein does,

and yet is all but laughed out of academia.

But in 1900 Bachelier publishes work that long after his death

will be recognised as groundbreaking.

His remarkable idea is that the price of government bonds follows a random walk,

meaning that each new movement in the price will be unpredictable, up or down.

That might seem odd.

Why would the performance of a financial asset be random?

But Bachelier understands that if it was obvious that a share or a bond

...