After the last ice age began, the number of animal species in Australia changed rapidly. The relationship between the elapsed time, $t$, in years, since the ice age began, and the total number of animal species, $S_{\text{year}}(t)$, is modeled by the following function: ###$S_{\text{year}}(t)=25{,}000{,}000\cdot \left(0.78\right)\^{\Large t}$ **Complete the following sentence about the rate of change in the number of species in *decades*.** *Round your answer to two decimal places.* Every ***decade***, the number of species decays by a factor of $\ $ [[☃ numeric-input 1]].