In attempting to identify bubbles before they burst, economists have developed a number of financial ratios and economic indicators that can be used to evaluate whether homes in a given area are fairly valued. By comparing current levels to previous levels that have proven unsustainable in the past (i.e. led to or at least accompanied crashes), one can make an educated guess as to whether a given real estate market is experiencing a bubble. Indicators describe two interwoven aspects of housing bubble: a valuation component and a debt (or leverage) component.