Of course, this statement is FALSE.
Let`s assume that a small town in Nevada had a population of 1,000.
When it lost 20% of its population:
1,000 * ( 1 - 0.2 ) = 1,000 - 0.8 = 800
After that the same town gained 20 % more people:
800 * ( 1 + 0.2 ) = 800 * 1.2 = 960
960 ≠ 1,000
In the end the town`s population was not the same as it was before the downturm.