First, let's calculate the absolute decrease: from 32500 to 28200 - that's 4300 people less.
Now, let's calculate the percentage:
[tex] \frac{4300}{32500}= \frac{43}{325}
[/tex]
which is approximately 0.132, and multipied by 100% it is 13.2 percent : so 13% is the correct answer.
