Migration

The following parameters determine aspects of population migration into and outside of a node, including daily commutes, seasonal migration, and one-way moves. Modes of transport includes travel by foot, automobile, sea, or air. Migration can also be configured to move all individuals in a family at the same time.

Note

Parameters are case-sensitive. For Boolean parameters, set to 1 for true or 0 for false. Minimum, maximum, or default values of “NA” indicate that those values are not applicable for that parameter.

EMOD does not use true defaults; that is, if the dependency relationships indicate that a parameter is required, you must supply a value for it. However, many of the tools used to work with EMOD will use the default values provided below.

JSON format does not permit comments, but you can add “dummy” parameters to add contextual information to your files. Any keys that are not EMOD parameter names will be ignored by the model.

Parameter

Data type

Minimum

Maximum

Default

Description

Example

Air_Migration_Filename

string

NA

NA

_add-your-air-migration-file_.json

The path to the input file that defines patterns of migration by airplane. Enable_Air_Migration must be set to true (1). See Migration files for information on migration files.

{
    "Migration_Model": "FIXED_RATE_MIGRATION",
    "Enable_Air_Migration": 1,
    "Air_Migration_Filename": "../Global_1degree_air_migration.bin"
}

Air_Migration_Roundtrip_Duration

float

0

10000

1

The average time spent (in days) at the destination node during a round-trip migration by airplane. Migration_Pattern must be set to SINGLE_ROUND_TRIPS.

{
    "Migration_Model": "FIXED_RATE_MIGRATION",
    "Enable_Air_Migration": 1,
    "Migration_Pattern": "SINGLE_ROUND_TRIPS",
    "Air_Migration_Roundtrip_Duration": 2
}

Air_Migration_Roundtrip_Probability

float

0

1

0.8

The likelihood that an individual who flies to another node will return to the node of origin during the next migration. Enable_Air_Migration must be set to true (1).

{
    "Migration_Model": "FIXED_RATE_MIGRATION",
    "Enable_Air_Migration": 1,
    "Air_Migration_Roundtrip_Probability": 0.9
}

Enable_Air_Migration

boolean

0

1

0

Controls whether or not migration by air travel will occur. Migration_Model must be set to FIXED_RATE_MIGRATION.

{
    "Migration_Model": "FIXED_RATE_MIGRATION",
    "Enable_Air_Migration": 1,
    "Air_Migration_Filename": "../inputs/air_migration.bin"
}

Enable_Family_Migration

boolean

0

1

0

Controls whether or not all members of a household can migrate together when a MigrateFamily event occurs. All residents must be home before they can leave on the trip. Migration_Model must be set to FIXED_RATE_MIGRATION.

{
    "Enable_Migration": "FIXED_RATE_MIGRATION",
    "Enable_Family_Migration": 1,
    "Family_Migration_Filename": "../inputs/family_migration.bin"
}

Enable_Local_Migration

boolean

0

1

0

Controls whether or not local migration (the diffusion of people in and out of nearby nodes by foot travel) occurs. Migration_Model must be set to FIXED_RATE_MIGRATION.

{
    "Migration_Model": "FIXED_RATE_MIGRATION",
    "Enable_Local_Migration": 1,
    "Local_Migration_Filename": "../inputs/local_migration.bin"
}

Enable_Migration_Heterogeneity

boolean

0

1

1

Controls whether or not migration rate is heterogeneous among individuals within each group that has a migration rate setting. Set to true (1) to apply a migration rate distribution (see NodeAttributes demographics parameters); set to false (0) to use the same migration rate applied to all individuals in the group. For example, if you are using a migration file that sets different migration rates for each age group in a node, you could apply an Gaussian distribution around a mean value in each age group or you could assign the same value to each individual in each age group.

Migration_Model must be set to FIXED_RATE_MIGRATION.

{
    "Migration_Model": "FIXED_RATE_MIGRATION",
    "Enable_Migration_Heterogeneity": 1
}

Enable_Regional_Migration

boolean

0

1

0

Controls whether or not there is migration by road or rail network into and out of nodes in the simulation. Migration_Model must be set to FIXED_RATE_MIGRATION.

{
    "Migration_Model": "FIXED_RATE_MIGRATION",
    "Enable_Regional_Migration": 1,
    "Regional_Migration_Filename": "../inputs/regional_migration.bin"
}

Enable_Sea_Migration

boolean

0

1

0

Controls whether or not there is migration on ships into and out of coastal cities with seaports. Migration_Model must be set to FIXED_RATE_MIGRATION.

{
    "Migration_Model": "FIXED_RATE_MIGRATION",
    "Enable_Sea_Migration": 1,
    "Sea_Migration_Filename": "../inputs/sea_migration.bin"
}

Local_Migration_Filename

string

NA

NA

_add-your-local-migration-file_.json

The path of the input file which defines patterns of migration to adjacent nodes by foot travel. See Migration files for information on migration files.

{
    "Local_Migration_Filename": "Local_Migration.bin"
}

Local_Migration_Roundtrip_Duration

float

0

10000

1

The average time spent (in days) at the destination node during a round-trip migration by foot travel. Migration_Pattern must be set to SINGLE_ROUND_TRIPS.

{
    "Enable_Local_Migration": 1,
    "Migration_Pattern": "SINGLE_ROUND_TRIPS",
    "Local_Migration_Roundtrip_Duration": 1.0
}

Local_Migration_Roundtrip_Probability

float

0

1

0.95

The likelihood that an individual who walks into a neighboring node will return to the node of origin during the next migration. Only used when Enable_Local_Migration is set to true (1).

{
    "Local_Migration_Roundtrip_Probability": 1.0
}

Migration_Model

enum

NA

NA

NO_MIGRATION

Model to use for migration. Possible values are:

NO_MIGRATION

Migration into and out of nodes will not occur.

FIXED_RATE_MIGRATION

Migration into and out of nodes will occur at a fixed rate as defined in the migration files. At the beginning of the simulation or whenever an individual has just moved, they pick their next destination and the time and type of the migration. If an individual is on an outbound leg of their journey, they will query the node’s MigrationInfo object and, through probability, pick a new destination; if the individual is inbound, they will travel back to their previous location.

{
    "Migration_Model": "FIXED_RATE_MIGRATION",
    "Local_Migration_Filename": "../inputs/local_migration.bin",
    "Enable_Local_Migration": 1
}

Migration_Pattern

enum

NA

NA

RANDOM_WALK_DIFFUSION

Describes the pattern of travel used during migration. Migration_Model must be set to FIXED_RATE_MIGRATION. Possible values are:

RANDOM_WALK_DIFFUSION

Individuals retain no memory of where they came from; every move is to a new destination with no thought of returning home.

SINGLE_ROUND_TRIPS

Individuals have a probability (determined Local_Migration_Roundtrip_Probability, Air_Migration_Roundtrip_Probability, etc.) that they will return to their original location after some duration of time. If they do not, the current location is the new departure point for migration, but their original location remains their home node.

WAYPOINTS_HOME

Individuals go on a multi-step journey along several waypoints and then retrace their steps back along their path once they have reached a maximum number of waypoints from their home node. For example, the path of travel would be 1 -> 2 -> 3 -> 4 -> 3 -> 2 -> 1 if their home is node 1. On the outbound journey, the duration at each waypoint is not set explicitly but is determined by each node’s migration rate; on the return journey, one timestep is spent at each waypoint.

{
    "Migration_Model": "FIXED_RATE_MIGRATION",
    "Migration_Pattern": "SINGLE_ROUND_TRIPS",
    "Enable_Local_Migration": 1,
    "Local_Migration_Roundtrip_Probability": 0.05,
    "Local_Migration_Roundtrip_Duration": 10
}

Regional_Migration_Filename

string

NA

NA

_add-your-regional-migration-file_.json

The path of the input file which defines patterns of migration by vehicle via road or rail network. If the node is not on a road or rail network, regional migration focuses on the closest hub city in the network. The file must be in .bin format. See Migration files for information on migration files.

{
    "Regional_Migration_Filename": "Regional_Migration.bin"
}

Regional_Migration_Roundtrip_Duration

float

0

10000

1

The average time spent (in days) at the destination node during a round-trip migration by road network. Migration_Pattern must be set to SINGLE_ROUND_TRIPS.

{
    "Enable_Regional_Migration": 1,
    "Migration_Pattern": "SINGLE_ROUND_TRIPS",
    "Regional_Migration_Roundtrip_Duration": 1.0
}

Regional_Migration_Roundtrip_Probability

float

0

1

0.1

The likelihood that an individual who travels by vehicle to another node will return to the node of origin during the next migration. Migration_Pattern must be set to SINGLE_ROUND_TRIPS.

{
    "Regional_Migration_Roundtrip_Probability": 1.0
}

Roundtrip_Waypoints

integer

0

1000

10

The maximum number of points reached during a trip before steps are retraced on the return trip home. Migration_Pattern must be set to WAYPOINTS_HOME.

{
    "Roundtrip_Waypoints": 5
}

Sea_Migration_Filename

string

NA

NA

_add-your-sea-migration-file_.json

The path of the input file which defines patterns of migration by ship. Only used when Enable_Sea_Migration is set to true (1). The file must be in .bin format. See Migration files for information on migration files.

{
    "Sea_Migration_Filename": "5x5_Households_Work_Migration.bin"
}

Sea_Migration_Roundtrip_Duration

float

0

10000

1

The average time spent at the destination node during a round-trip migration by ship. Used only when Migration_Pattern must be set to SINGLE_ROUND_TRIPS.

{
    "Enable_Sea_Migration": 1,
    "Migration_Pattern": "SINGLE_ROUND_TRIPS",
    "Sea_Migration_Roundtrip_Duration": 10000
}

Sea_Migration_Roundtrip_Probability

float

0

1

0.25

The likelihood that an individual who travels by ship into a neighboring node will return to the node of origin during the next migration. Used only when Enable_Sea_Migration is set to true (1).

{
    "Sea_Migration_Roundtrip_Probability": 0
}

x_Air_Migration

float

0

3.40E+38

1

Scale factor for the rate of migration by air, as provided by the migration file. Enable_Air_Migration must be set to 1.

{
    "Scale_Factor_Air_Migration": 1
}

x_Family_Migration

float

0

3.40E+38

1

Scale factor for the rate of migration by families, as provided by the migration file. Enable_Family_Migration must be set to true (1).

{
    "x_Family_Migration": 1
}

x_Local_Migration

float

0

3.40E+38

1

Scale factor for rate of migration by foot travel, as provided by the migration file. Enable_Local_Migration must be set to 1.

{
    "x_Local_Migration": 1
}

x_Regional_Migration

float

0

3.40E+38

1

Scale factor for the rate of migration by road vehicle, as provided by the migration file. Enable_Regional_Migration must be set to 1.

{
    "x_Regional_Migration": 1
}

x_Sea_Migration

float

0

3.40E+38

1

Scale factor for the rate of migration by sea, as provided by the migration file. Enable_Sea_Migration must be set to 1.

{
    "x_Sea_Migration": 1
}