Can governments measure happiness by survey?

In opposition, David Cameron was keen on measuring happiness - or "economic well-being" - which should be good news to the people of Northern Ireland, revealed as the happiest in the UK at last week's PMQs.

Tim Harford, also known as the FT's undercover economist and the presenter of Radio 4's More or Less, explains the mechanics of measuring happiness, and reveals which cheers people up the most - shopping or praying.

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