Elasticity measures the responsiveness of quantity demanded to a price change. It is given by the formula % change in quantity demanded / % change in price – which yields a number (which is not value of anything, just a ratio). So 20%/10% would yield the number 2 – implying elastic (responsive) demand). Sales go up/go down by twice as much as the price fall/rise. Housing (below) has a very low elasticity value of 0.12, implying demand is unresponsive to price changes.