Nataraj $(2007)$ finds that a $80\%$ increase in the price of water for heavy users in Santa Cruz caused the quantity of water they demanded to fall by an average of $20\%.($Before the increase, heavy users initially paid $$1\mathrm{.}55$ per unit, but afterwards they paid $$2\mathrm{.}79$ per unit.$)$ In percentage terms, how much did their water expenditure $($price times quantity$)$which is the water company's revenue$$change$?$

With the price increase, the company's revenue changed by $\%.($Enter your answer rounded to two decimal places.$)$