A housing bubble, or real estate bubble, is a run-up in housing prices fueled by demand, speculation, and exuberant spending to the point of collapse. Housing bubbles usually start with an increase in demand, in the face of limited supply, which takes a relatively extended period to replenish and increase. Speculators pour money into the market, further driving up demand. At some point, demand decreases or stagnates at the same time supply increases, resulting in a sharp drop in prices—and the bubble bursts.