Being unemployed is even more disastrous for individuals than you'd expect. Aside from the obvious harm - poverty, difficulty paying off debts - it seems to directly affect people's health, particularly that of older workers.

Campaigns fail if they waste resources courting voters who are unpersuadable or already persuaded. Their most urgent task is to find and persuade the few voters who are genuinely undecided and the larger number who are favorably disposed but need a push to actually vote.

Lack of confidence, sometimes alternating with unrealistic dreams of heroic success, often leads to procrastination, and many studies suggest that procrastinators are self-handicappers: rather than risk failure, they prefer to create conditions that make success impossible, a reflex that of course creates a vicious cycle.

Corporations hope that the right concept will turn things around overnight. This is what you might call the crash-diet approach: starve yourself for a few days and you'll be thin for life.

The fact that cognitive diversity matters does not mean that if you assemble a group of diverse but thoroughly uninformed people, their collective wisdom will be smarter than an expert's. But if you can assemble a diverse group of people who possess varying degrees of knowledge and insight, you're better off entrusting it with major decisions rather than leaving them in the hands of one or two people, no matter how smart those people are.

In part because individual judgement is not accurate enough or consistent enough, cognitive diversity is essential to good decision making.

In industries where a lot of competitors are selling the same product - mangoes, gasoline, DVD players - price is the easiest way to distinguish yourself. The hope is that if you cut prices enough you can increase your market share, and even your profits. But this works only if your competitors won't, or can't, follow suit.