"In the stock market — or the housing market, for that matter — people often struggle to think more than one or two steps ahead. That’s a big reason that bubbles can form. It was true that a lot of dot-com companies from the 1990s were on to something new and important, just as it was true that housing prices rarely fall. But if everybody else decides that dot-com stocks and houses are a great investment, a problem can easily develop. The prices of those assets can rise so high that they’re no longer a good value."
Try this 'one question' quiz Puzzle: Are You Smarter Than 48,910 Other New York Times Readers?http://www.nytimes.com/interactive/2015/08/13/upshot/are-you-smarter-than-other-new-york-times-readers.html