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My name's Linda Davies and I Commission Podcasts for BBC Sounds.

As you'd expect, at the BBC we make podcasts of the very highest quality featuring the most knowledgeable

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Hello and welcome to more or less, your guide to numbers in the news and in life.

I'm Tim Harford. How much is a thing worth an ounce of gold, a share in

apple a kilogram of apples? What's its value? This is one of the key questions in economics. We start learning about it in the playground,

a banana and a cheese string for a chocolate biscuit, seven random stickers for that shiny

of Leonel messy that's missing from your World Cup album.

But sometimes the market gets things wrong, and this is particularly true of a financial market.

In a regular market market you usually buy a

kilogram of apples to eat the apples rather than to resell them at a profit, but

financial markets are different. You buy a share of Apple because you've taken a view about the

future prospects for that company and its shares. Sometimes we overestimate the worth of a

product and the price is driven up and then as more and more investors decide to

pile in an attempt to make a quick buck the cost rises higher and higher until demand

collapses the bubble bursts and the price crashes. It's called a speculative bubble, and over the last few

hundred years, whenever we see something that we fear could end this way, there's one famous example we bring out again and again as a warning

from history about the dangers of greed.

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