5.6. Step 6: Base Emigration

5.6.1. Model Description

At this step we add a module for emigration based on age, sex and district of residence. This is the base version of emigration resembling a typical macro population projection approach. It will be complemented with refined models going beyond age and sex when modeling emigration.

5.6.2. The new module: EmigrationAgeSexDistrict.mpp

This module implements a base version of emigration. It is based on age, sex,and district based emigration rates, which is a typical approach in cohort-component models. The module can be switched on/off by the user. People who emigrate are removed from the population.

The module is prepared for being replaced by a refined model accounting for more detailed personal characteristics than age and sex and/or allowing for return migration. For this purpose a logical state use_base_emigration_model is introduced and initialized with TRUE; Other modules can override this module by setting the state to FALSE whenever an alternative model is applied.

////////////////////////////////////////////////////////////////////////////////////////////////////
// Parameters
////////////////////////////////////////////////////////////////////////////////////////////////////

parameters
{
    //EN Switch emigration on/off
    logical     ModelEmigration;

    //EN Emigration rates on district level
    double  EmigrationRatesDistrict[SEX][AGE5_PART][DISTRICT_NAT];
};

parameter_group PG_EmigrationBase  //EN Emigration Base Version
{
    ModelEmigration, EmigrationRatesDistrict
};

////////////////////////////////////////////////////////////////////////////////////////////////////
// Actor bloc
////////////////////////////////////////////////////////////////////////////////////////////////////

actor Person
{
    logical use_base_emigration_model = { TRUE };           //EN Use base model version
    logical has_emigrated = { FALSE };                      //EN Person has emigrated
    event   timeEmigrationEvent, EmigrationEvent;           //EN Emigration event
};

////////////////////////////////////////////////////////////////////////////////////////////////////
// Implementation
////////////////////////////////////////////////////////////////////////////////////////////////////

TIME Person::timeEmigrationEvent()
{
    if (ModelEmigration && is_resident && in_projected_time && use_base_emigration_model &&
        EmigrationRatesDistrict[sex][SPLIT(integer_age, AGE5_PART)][district_nat] > 0.0)
    {
        return WAIT(-log(RandUniform(10)) /
            EmigrationRatesDistrict[sex][SPLIT(integer_age, AGE5_PART)][district_nat]);
    }
    else return TIME_INFINITE;
}

void Person::EmigrationEvent()
{
    district_int = DISTI_ABROAD;
    has_emigrated = TRUE;
    Finish();
}