## HDSS Migration Data

The indicators available are Crude in-migration rate (CIMR), Crude out-migration rate (COMR), Age-specific in-migration rates (ASIMR), Age-specific out-migration rates (ASOMR), Crude net-migration rate (CNMR) and Crude gross-migration rate (CGMR).

**Migration**

Migration is defined as a change of residence. Minimum time to be considered a resident varies from one HDSS to the other but a standard of six months have been adopted for INDEPTHStats (see Population). In-migrants are residents after they have spent more than six months in the demographic surveillance area. Out-migrants are no longer residents after they have spent more than six months outside the demographic surveillance area.

**Crude in-migration rate (CIMR)**

CIMR is the number of in-migrations divided by the person-years of all ages, expressed in in-migrations per 1000 person-years.

NB: CIMR depends on age-structure, which evolves from one calendar year to the next and from one HDSS to the other. Therefore CIMRs are not strictly comparable over the period and across HDSS.

**Crude out-migration rate (COMR)**

COMR is the number of out-migrations divided by the person-years of all ages, expressed in out-migrations per 1000 person-years.

NB: COMR depends on age-structure, which evolves from one calendar year to the next and from one HDSS to the other. Therefore COMRs are not strictly comparable over the period and across HDSS.

**Age-specific in-migration rates (ASIMR)**

ASIMR is the number of in-migrations in a specific age-group divided by the person-years lived in that age-group, expressed in in-migrations per 1000 person-years.

**Age-specific out-migration rates (ASOMR)**

ASOMR is the number of out-migrations in a specific age-group divided by the person-years lived in that age-group, expressed in out-migrations per 1000 person-years.

**Crude net-migration rate (CNMR)**

CNMR is the number of in-migrations minus out-migrations divided by the person-years of all ages, expressed in net-migrations per 1000 person-years. CNMR may be positive or negative.

NB: CNMR depends on age-structure, which evolves from one calendar year to the next and from one HDSS to the other. Therefore CNMRs are not strictly comparable over the period and across HDSS.

**Crude gross-migration rate (CGMR)**

CGMR is the number of in-migrations plus out-migrations divided by the person-years of all ages, expressed in migrations per 1000 person-years.

NB: CGMR depends on age-structure, which evolves from one calendar year to the next and from one HDSS to the other. Therefore CGMRs are not strictly comparable over the period and across HDSS.