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Population Growth Dynamics at Household

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- Earlier:
- Population growth occurred via reproduction only in the Farming unit if there is one.
- Ignores the reproduction in herding and labor activates.
- While lack of reproduction while herding is reasonable, we may need to consider reproduction while herding unit is at household and reproduction in labor activity.

- Now:
- Population growth occurs at the activity level.
- Splitting decision occurs at the Household level.
- Considers reproduction in Farming, Labor activities. Also, considers reproduction in Herding activity when herding unit is at the household.

- Slash-N-Burn or Low Intensity Farming
- Low Yield Rate (Currently it is set to 2)
- Household which adopt this type of farming also have herding and labor activities.
- Household survival is kind of robust to changes in weather because of the presence of other activities that can feed people in the household in adverse situations that do not support farming.

- High Intensity Farming
- High Yield Rates (between 2to 12).
- Yield rates depend upon the number of people involved in farming. So the yield rate is different for different farming units with different farming populations.
- Household survival is sensitive to changes in weather. Mass displacement is expected from these parcels in adverse weather situations like persistent droughts.

Farming

- A parcel can accommodate up to 100 High Intensity Farming Units.
- Households that adopt high intensity farming do not have herding units.
- Farmable area is set and fixed at 1 hectare per Farming unit.

- Efficiency of Farming:
- Modeled using a generalized logistic equation
- n = Number of Farmers
- L = Lower Asymptote
(2 in the model when n < 1)

- U = Upper Asymptote
(20in the model when n > 10)

- Fixed Household initialization which was considering parcel population to initialize household size. Now, the initial population is set by choosing from a discrete uniform distribution over [6 , 12].
- Household splitting is moved to household from activities. Minimum household size for considering splitting is determined randomly for each household by drawing an integer in [9,13] with uniform probability.
- Modeling of two types of Farming facilitates experimenting with realistic population in the model.
- Riftland’s rural population: 69,283,092
- Calculated by marking all parcels with population greater than 1000 as urban.
- Also, excluded population on parcels that are marked as Park Land or Forest.

- Fixing Herding so as to reproduce reasonable behavior in the context of high population densities. This in turn will slow down the model a little.
- Need to determine realistic reproduction rates. Possibly via discussion with HRAF or from literature or from both (Tim & Bill).
- Produce displacement data by running entire Riftland model with realistic number of households and population. This may take ≈ 1-2 days of running time.
- Given the observed tick rate, the model as it is now will take ≈14 hrs to complete 4320 steps (12 years for which we have rainfall data) if everything stay the same (which will not happen as households split and so on).