We can calculate a percent change by calculating the difference between the actual state and the previous state and then dividing this difference by the previuos state.
Finally, multypling by 100% gives the percentage change.
Here we have the last state as the future population (4823 thousand people). The actual state (in this case the state to which wew want to compare the variation ir change) is 5700 thousand people.
The difference is 4823 - 5700 = -877.
Then, we can divide it by the actual population and we will have:

This is equivalent to:

If we have to round to nearest tenth, the percent change is 15.4%.