Every day we make countless decisions, from the small, mundane things to tackling life's big questions, but we don't always make the right choices.

Behavioural scientist Dr David Halpern heads up Number 10's 'Nudge Unit', the world's first government institution that uses behavioural economics to examine and influence human behaviour, to 'nudge' us into making better decisions. Seemingly small and subtle solutions have led to huge improvements across tax, healthcare, pensions, employment, crime reduction, energy conservation and economic growth.

Adding a crucial line to a tax...