While they appear to have little in common, time and money are frequently interchangeable. Researchers refer to the amount of time that people spend in an unpleasant mood - when feelings of tension, depression or irritation outweigh feelings of happiness - as the 'U-index'. For instance, people are rarely in an unpleasant mood while exercising, reading or praying; but unpleasant moods are common while working, commuting and doing housework. Sadly, over the past 50 years, the overall U-index has barely budged. The authors show that by re-allocating our time in three key areas - commuting, watching television and spending time with loved ones-we can impact our happiness in a more powerful way than money every can.

Employees who spend some or all of their bonuses on others-thereby creating what the authors call a "prosocial" workplace-are happier as a result. Managers can enhance that effect by providing opportunities to share the wealth.