The quantity demanded generally decreases when the
price increases, so this ratio is usually expected to be
negative. For example, if a 10% increase in the price of
good A results in a 6% fall in the quantity demanded of
that good, its own price elasticity is -0.6. By contrast, if a
10% fall in the price of good B leads to a 12% increase in
the quantity demanded of good B, its own price elasticity
is -1.2