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.

Every time you log in to Facebook, every time you click on your News Feed, every time you Like a photo, every time you send anything via Messenger, you add another data point to the galaxy they already have regarding you and your behavior.