Charles Duhigg

There is a woman named Wendy Wood, who did a study when she was at Duke, and she followed around college students to try to figure out how much of their day was decision-making versus how much was habit. And what she found was that about 45 percent of all the behaviors that someone did in a day was habit.

As homeowners see the value of their homes decline, they become more likely to delay purchases of the big items - like automobiles, electronics and home appliances - that are ballasts of the American economy. When those purchases decline, large manufacturing firms, suddenly short on funds, could begin laying off employees.

In 1967, the world health community launched a global effort to eradicate smallpox. It took a coordinated, worldwide effort, required the commitment of every government, and cost $130 million dollars. By 1977, smallpox had disappeared.