When it comes to market bubbles and how they are created, very little, if anything, has changed. This is because human psychology has not changed. Massive bubbles are created when large numbers of people buy into "new era" stories that exaggerate how much the world has improved. For example, in the past few years the global equities and housing bubbles were driven by a giddy faith that world markets were on a tear and prices would go up indefinitely. Our animal spirits are sparked by these tales; we find them irresistible. And since as animals we're also given to a herd mentality, in a bubble we tend to invest too much in the most popular stories--and continue to do so even after the bubble bursts.