Population for the scenario years is calculated with the following formula:

Pn | = | Pb * (1+ G/100)^{N} + M |

with |
||

Pn | = | new Population |

Pb | = | Population of previous time step |

G | = | Annual Growth rate in % |

N | = | Timestep, usually 5 (years) |

M | = | Migration (in absolute numbers) |

The previously applied formula

Pn | = | Pb * e^{G/100 *N} + M |

proved as being mathematically wrong and has been discarded.

The annual results of the population forecasts are stored in table STP_POPULATION.

**Notes on Parameters**:

**Timestep N**. Usually 5 years except for 2005. For that year, N is the difference between 2005 and the reference year for which billing data are applied.

**Migration** is the assumed total migration in or out of the selected DCs between the years for which demands are to be calculated. Since the time *between* the balancing years is of no interest, it is sufficient to enter M only for the balancing years. Usually Migration does not apply to a large selection of Demand Centers!

The general concept of growthrate and migration is widely applied in the pre-processing module.