How about 2000 * (1.3 ^ 4) ?
or to state as a formula where p is initial population, g is annual % growth and y is number of years:
p * (((100 + g) / 100) ^ y)
However, I am probably over simplifying here as population will be growing continually throughout the year and at any point in the year, growth will be 30 % of that population per annum (hmm need "my ears are bleeding smiley) . If we turn it in to say, an interest on savings question where interest is calculated once a year, then I think the formula is valid.