# Population dynamics¶

The following parameters determine characteristics related to population dynamics, such as age distribution, births, deaths, and gender. The values set here generally interact closely with values in the demographics file.

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

Age_Initialization_Distribution_Type

enum

NA

NA

DISTRIBUTION_OFF

The method for initializing the age distribution in the simulated population. Possible values are:

DISTRIBUTION_OFF

All individuals default to age 20 years old.

DISTRIBUTION_SIMPLE

Individual ages are drawn from a distribution whose functional form is specified in the demographics file using the IndividualAttributes simple Age distribution parameters.

DISTRIBUTION_COMPLEX

Individual ages are drawn from a piecewise linear function specified in the demographics file complex distribution parameters.

{
"Age_Initialization_Distribution_Type": "DISTRIBUTION_SIMPLE"
}


Birth_Rate_Boxcar_Forcing_Amplitude

float

0

3.40E+38

0

Fractional increase in birth rate during high birth season when Birth_Rate_Time_Dependence is set to ANNUAL_BOXCAR_FUNCTION.

{
"Enable_Vital_Dynamics": 1,
"Enable_Birth": 1,
"Birth_Rate_Time_Dependence": "ANNUAL_BOXCAR_FUNCTION",
"Birth_Rate_Boxcar_Forcing_Amplitude": 0.1
}


Birth_Rate_Boxcar_Forcing_End_Time

float

0

365

0

Day of the year when the high birth rate season ends when Birth_Rate_Time_Dependence is set to ANNUAL_BOXCAR_FUNCTION.

{
"Enable_Vital_Dynamics": 1,
"Enable_Birth": 1,
"Birth_Rate_Time_Dependence": "ANNUAL_BOXCAR_FUNCTION",
"Birth_Rate_Boxcar_Forcing_End_Time": 220
}


Birth_Rate_Boxcar_Forcing_Start_Time

float

0

365

0

Day of the year when the high birth rate season begins when Birth_Rate_Time_Dependence is set to ANNUAL_BOXCAR_FUNCTION.

{
"Enable_Vital_Dynamics": 1,
"Enable_Birth": 1,
"Birth_Rate_Time_Dependence": "ANNUAL_BOXCAR_FUNCTION",
"Birth_Rate_Boxcar_Forcing_Start_Time": 130
}


Birth_Rate_Dependence

enum

NA

NA

FIXED_BIRTH_RATE

The method used to modify the value set in BirthRate in the demographics file (see NodeAttributes parameters). Possible values are:

NONE

Births are not allowed during the simulation, even if Enable_Birth is set to true (1).

FIXED_BIRTH_RATE

The absolute rate at which new individuals are born, as set by BirthRate.

POPULATION_DEP_RATE

Scales the node population to determine the birth rate. If BirthRate is greater than 0.005, a value of 2% per year (0.02/365) is used instead.

DEMOGRAPHIC_DEP_RATE

Scales the female population within fertility age ranges (15-44 years) to determine the birth rate. If BirthRate is greater than 0.005, a value of 1 child every 8 years of fertility [1/8/365(~0.000342)] is used instead.

INDIVIDUAL_PREGNANCIES

Scales the female population within fertility age ranges (15-44 years) to determine the birth rate, but pregnancies are assigned on an individual basis and result in a 40-week pregnancy for a specific individual with a birth at the end.

INDIVIDUAL_PREGNANCIES_BY_AGE_AND_YEAR

Similar to INDIVIDUAL_PREGNANCIES, but determines the rate based on the FertilityDistribution (in IndividualAttributes), using the individual’s age and the year of the simulation.

{
"Enable_Vital_Dynamics": 1,
"Enable_Birth": 1,
"Birth_Rate_Dependence": "POPULATION_DEP_RATE"
}


Birth_Rate_Sinusoidal_Forcing_Amplitude

float

0

1

0

The amplitude of sinusoidal variations in birth rate when Birth_Rate_Time_Dependence is set to SINUSOIDAL_FUNCTION_OF_TIME.

{
"Enable_Vital_Dynamics": 1,
"Enable_Birth": 1,
"Birth_Rate_Time_Dependence": "SINUSOIDAL_FUNCTION_OF_TIME",
"Birth_Rate_Sinusoidal_Forcing_Amplitude": 0.1
}


Birth_Rate_Sinusoidal_Forcing_Phase

float

0

365

0

The phase of sinusoidal variations in birth rate. Birth_Rate_Time_Dependence must be set to SINUSOIDAL_FUNCTION_OF_TIME.

{
"Birth_Rate_Sinusoidal_Forcing_Phase": 20
}


Birth_Rate_Time_Dependence

enum

NA

NA

NONE

A scale factor for BirthRate that allows it to be altered by time or season. Enable_Birth must be set to true (1). Possible values are:

NONE

Birth rate does not vary by time.

SINUSOIDAL_FUNCTION_OF_TIME

Allows birth rate to be time-dependent, following a sinusoidal shape defined by $$1 + \sin \text{Birth\_Rate\_Sinusoidal\_Forcing\_Amplitude} \times \sin(2 \pi \times (\text{day} - \sin \text{Birth\_Rate\_Sinusoidal\_Forcing\_Phase})/365)$$. Set Birth_Rate_Sinusoidal_Forcing_Amplitude and Birth_Rate_Sinusoidal_Forcing_Phase.

ANNUAL_BOXCAR_FUNCTION

Allows birth rate to follow a boxcar function. The scale factor will be equal to 1 except for a single interval in which it is equal to a given constant equal to 1 + Birth_Rate_Boxcar_Forcing_Amplitude. Set Birth_Rate_Boxcar_Forcing_Amplitude, Birth_Rate_Boxcar_Forcing_End_Time, and Birth_Rate_Boxcar_Forcing_Start_Time.

{
"Enable_Vital_Dynamics": 1,
"Enable_Birth": 1,
"Birth_Rate_Time_Dependence": "ANNUAL_BOXCAR_FUNCTION"
}


Death_Rate_Dependence

enum

NA

NA

NOT_INITIALIZED

Determines how likely individuals are to die from natural, non-disease causes. Enable_Natural_Mortality must be set to 1. Possible values are:

NOT_INITIALIZED

The daily mortality rate is 0, and no one dies from non-disease related causes.

NONDISEASE_MORTALITY_BY_AGE_AND_GENDER

The individual’s age and gender are taken into account to determine the daily mortality rate.

NONDISEASE_MORTALITY_BY_YEAR_AND_AGE_FOR_EACH_GENDER

Gender, age, and year, are all taken into account to determine the daily mortality rate.

Properties, rates, and bin sizes can be set for non-disease mortality for each gender in the demographics file (see Complex distributions parameters).

{
"Death_Rate_Dependence": "NONDISEASE_MORTALITY_BY_AGE_AND_GENDER"
}


Default_Geography_Initial_Node_Population

integer

0

1000000

1000

When using the built-in demographics for default geography, the initial number of individuals in each node. Note that the built-in demographics feature does not represent a real geographical location and is mostly used for testing. Enable_Demographics_Builtin must be set to true (1).

{
"Enable_Demographics_Builtin": 1,
"Default_Geography_Initial_Node_Population": 1000,
"Default_Geography_Torus_Size": 3
}


Demographics_Filenames

array of strings

NA

NA

An array of the paths to demographics files containing information on the identity and demographics of the region to simulate. The files must be in .json format. Note that this parameter is only required when Enable_Demographics_Builtin is set to 0.

{
"Demographics_Filenames": [
"Namawala_single_node_demographics.json",
"Namawala_demographics_overlay.json"
]
}


Enable_Aging

boolean

0

1

1

Controls whether or not individuals in a population age during the simulation. Enable_Vital_Dynamics must be set to true (1).

{
"Enable_Vital_Dynamics": 1,
"Enable_Aging": 1
}


Enable_Birth

boolean

0

1

1

Controls whether or not individuals will be added to the simulation by birth. Enable_Vital_Dynamics must be set to true (1). If you want new individuals to have the same intervention coverage as existing individuals, you must add a BirthTriggeredIV to the campaign file.

{
"Enable_Vital_Dynamics": 1,
"Enable_Birth": 1
}


Enable_Demographics_Birth

boolean

0

1

0

Controls whether or not newborns have disease risk drawn from a distribution; uniform disease risk if false. Enable_Birth, Enable_Demographics_Risk, and Enable_Vital_Dynamics must be set to true (1).

{
"Enable_Birth": 1,
"Enable_Demographics_Birth": 1,
"Enable_Vital_Dynamics": 1
}


Enable_Demographics_Builtin

boolean

0

1

0

Controls whether or not built-in demographics for default geography will be used. Note that the built-in demographics feature does not represent a real geographical location and is mostly used for testing. Set to true (1) to define the initial population and number of nodes using Default_Geography_Initial_Node_Population and Default_Geography_Torus_Size. Set to false (0) to use demographics input files defined in Demographics_Filenames.

{
"Enable_Demographics_Builtin": 1,
"Default_Geography_Initial_Node_Population": 1000,
"Default_Geography_Torus_Size": 3
}


Enable_Demographics_Risk

boolean

0

1

0

Controls whether or not the simulation includes the impact of disease risk in demographics.

{
"Enable_Demographics_Risk": 1
}


Enable_Vital_Dynamics

boolean

0

1

1

Controls whether or not births and deaths occur in the simulation. Births and deaths must be individually enabled and set.

{
"Enable_Vital_Dynamics": 1,
"Enable_Birth": 1,
"Death_Rate_Dependence": "NOT_INITIALIZED",
"Base_Mortality": 0.002
}


float

0

3.40E+38

15

The age, in years, after which an individual is considered an adult. Individual_Sampling_Type must be set to ADAPTED_SAMPLING_BY_AGE_GROUP.

{
}


Population_Density_Infectivity_Correction

enum

NA

NA

CONSTANT_INFECTIVITY

Correction to alter infectivity by population density set in the Population_Density_C50 parameter. Measured in people per square kilometer. Possible values are:

• CONSTANT_INFECTIVITY

• SATURATING_FUNCTION_OF_DENSITY

Note

Sparsely populated areas have a lower infectivity, while densely populated areas have a higher infectivity, which rises to saturate at the Base_Infectivity value.

{
"Population_Density_Infectivity_Correction": "SATURATING_FUNCTION_OF_DENSITY"
}


Population_Scale_Type

enum

NA

NA

USE_INPUT_FILE

The method to use for scaling the initial population specified in the demographics input file. Possible values are:

USE_INPUT_FILE

Turns off population scaling and uses InitialPopulation in the demographics file (see NodeAttributes parameters).

FIXED_SCALING

Enables Base_Population_Scale_Factor.

{
"Population_Scale_Type": "FIXED_SCALING"
}


x_Base_Population

float

0

3.40E+38

1

Scale factor for InitialPopulation in the demographics file (see NodeAttributes parameters). If Population_Scale_Type is set to FIXED_SCALING, the initial simulation population is uniformly scaled over the entire area to adjust for historical or future population density.

{
"x_Base_Population": 0.0001
}


x_Birth

float

0

3.40E+38

1

Scale factor for birth rate, as provided by the demographics file (see NodeAttributes parameters). Enable_Birth must be set to 1.

{
"x_Birth": 1
}