Bubble

In markets, a bubble is an extended period of extreme overvaluation. Bubbles occur in stock markets, real estate, commodities and precious metals. There have even been bubbles in the flower market, the most famous example being the Dutch Tulip Mania of the seventeenth century. Bubbles are formed when excessive speculation enters a market. Instead of viewing the intrinsic value of an asset, speculators in a bubble market instead focus on the resale value of the asset. This is sometimes referred to as the greater fool theory of investing. In a bubble, it doesn't seem to matter that a price is irrationally high - it only matters that it can be sold for an even more irrational price at a later date. Bubbles often end with steep declines, where most of the speculative gains are quickly wiped out.