How long of a time period? Is 20 years sufficient? 200 years? Historically, most empires rose to greatness and then imploded in fewer than 200 years. So I guess

How long of a time period? Is 20 years sufficient? 200 years? Historically, most empires rose to greatness and then imploded in fewer than 200 years. So I guess we shouldn't look over too long a time period. We've enjoyed the repercussions of the United States' rapid ascent from a fledgling colony to a world superpower. If we look at the stock market during this period of remarkable growth, it's very easy to conclude that markets will always go up. Of course, this would be a very foolish conclusion.