the fact that the population has zero population growth over a year means that, if at the start of the year the population was X, at the end of the year the population, Y, can't be bigger than X.
Then the relation between the population at the end of the year, Y, and the start of the year, X, is:
It must be the same or less. Depending on if population growth means just how much it got bigger of if it can be negative (like -8% means it got smaller by 8% and being considered "growth").
