/**
* Updates population for given year based on formula in spec
*
* @param year year for which to calculate population
*/
public void updatePopulation(int year) {
population[year - START_YEAR] = 0;
for (AgriculturalUnit unit : entities) {
unit.updatePopulation(year);
population[year - START_YEAR] += unit.getPopulation(year);
}
}
