Answer
$$ 59.0\%$$
Work Step by Step
We see that the population in the year 2000 is 6.1 billion. We see that the population in the year 2050 is 9.7 billion. Thus, the percent change in population is:
$$ =(\frac{9.7}{6.1} -1 )\times 100\% \\ = (1.59-1)\times 100\% \\ = 59.0\%$$