From a lovely piece about the state of the British economy by John Lanchester in the London Review of Books:
“About thirty years ago, when Keynes was in the depths of economic unfashionability, going up to a group of macroeconomists and trying to start a conversation about the multiplier would have been roughly like going up to a group of astrophysicists and trying to start a conversation about your star sign.”
The multiplier and GDP is well explained earlier in the same piece:
“Imagine for a moment that you come across an unexpected ten pounds. After making a mental note not to spend it all at once, you go out and spend it all at once, on, say, two pairs of woolly socks. The person from the sock shop then takes your tenner and spends it on wine, and the wine merchant spends it on tickets to see The Bitter Tears of Petra von Kant, and the owner of the cinema spends it on chocolate, and the sweet-shop owner spends it on a bus ticket, and the owner of the bus company deposits it in the bank. That initial ten pounds has been spent six times, and has generated £60 of economic activity. In a sense, no one is any better off; and yet, that movement of money makes everyone better off. To put it another way, that first tenner has contributed £60 to Britain’s GDP. Seen in this way, GDP can be thought of as a measure not so much of size – how much money we have, how much money the economy contains – but of velocity. It measures the movement of money through and around the economy; it measures activity. If you had taken the same ten quid when it was first given to you and simply paid it into your bank account, the net position could be argued to be the same – except that the only contribution to GDP is that initial gift of £10, and if this behaviour were replicated across the whole economy, then the whole economy would grind to a halt. And that, broadly speaking, is what is happening right now. People are sitting on that first tenner.”
