we dropped the distinction too Interviews to elicit empirical data about friendship network Whom do you most enjoy to spend time with? What do you do together, how do you know each other? Restricted to 4 people, not living in the same household 29 women, 19 men => Types of relationships identified Relative, same church, work together, neighbour, went to school together => Friends are of the same gender => Empirical network itself not useable">

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CAVES Project Meeting September 2007 ● CPM1 South African Case Study Model Report Shah Jamal Alam, Ruth Meyer, Scott Moss Centre for Policy Modelling,

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Presentation on theme: "CAVES Project Meeting September 2007 ● CPM1 South African Case Study Model Report Shah Jamal Alam, Ruth Meyer, Scott Moss Centre for Policy Modelling,"— Presentation transcript:

1 CAVES Project Meeting September 2007 ● CPM1 South African Case Study Model Report Shah Jamal Alam, Ruth Meyer, Scott Moss Centre for Policy Modelling, MMU

2 CAVES Project Meeting September 2007 ● CPM2 Table of Contents Results from the Field Trip Declarative Model Current state of the model Experiences with Jess Next steps Procedural Model Dynamic Networks Analysis

3 CAVES Project Meeting September 2007 ● CPM3 Findings from the Field Trip Friendship Network People do not distinguish between "friend" and "acquaintance" => we dropped the distinction too Interviews to elicit empirical data about friendship network Whom do you most enjoy to spend time with? What do you do together, how do you know each other? Restricted to 4 people, not living in the same household 29 women, 19 men => Types of relationships identified Relative, same church, work together, neighbour, went to school together => Friends are of the same gender => Empirical network itself not useable

4 CAVES Project Meeting September 2007 ● CPM4 Declarative Model Integration of further processes that influence social networks Burial societies Revision of stokvels Borrowing of food/money Marriage Education Spread of HIV/AIDS on an individual basis

5 CAVES Project Meeting September 2007 ● CPM5 Declarative Model – Burial Societies Burial societies are formed between groups of relatives, neighbours and/or friends They may already exist at the start of the simulation or they may be formed during the simulation Have a high priority for households Fees are second after food Ask for grace period if necessary (up to 5 months) A household head tries to join a burial society if No-one in the household is a member yet Enough money left at the end of the month If there are burial societies, will join the cheapest one If there aren't, will try to start one If a member dies the new household head will try to continue the membership

6 CAVES Project Meeting September 2007 ● CPM6 Declarative Model – Stokvels Stokvels are formed between groups of friends If there are no stokvels amongst the friends, try to start one When enough (> 4) friends mutually express the desire to from a stokvel If there are stokvels, join the one most of the friends belong to Rules: Single adult males with employment will try to join a stokvel to save up for lobola Married adult males with employment still living in their parents’ household will join a stokvel to save up for a house Adult females will try to join a stokvel to save up for (their) childrens’ education, i.e. when there are children over the age of 14 in the household

7 CAVES Project Meeting September 2007 ● CPM7 Declarative Model – Stokvels/Burial Societies Rules for formation, grace periods and disbanding are similar for stokvels and burial societies Need >= 4 friends to start Disband when < 4 members left Allow people to skip paying the monthly fee for a while "Grace period" Have to pay back accumulated debts Rules for pay-out are different since the groups are different types of savings clubs Burial societies pay out for death of member / death of covered person (= member of a member's household) Stokvels pay out accumulated savings after a turn Burial societies are prioritised over stokvels in household expenditure => Stokvels tend to be smaller but more numerable => Burial societies are more stable, stokvels tend to dissolve more easily

8 CAVES Project Meeting September 2007 ● CPM8 Declarative Model – Borrowing Food Poor households will ask relatives and neighbours for help If they can't afford to buy enough food at the beginning of a month Send each relative/neighbour household a request Rich(er) households will try to help out If enough cash after they paid for their own food and other commitments If they "feel" obliged to Modelled as probability Give random amount between 10 Rand and half the needed amount Poor households will buy additional food with the received gifts No pay-back yet

9 CAVES Project Meeting September 2007 ● CPM9 Declarative Model – Borrowing Food

10 CAVES Project Meeting September 2007 ● CPM10 Declarative Model – Problems with Household Economy Households become very rich Income from Government jobs: 4% of adults, 800 to 1600 Rand monthly Piece jobs: occasionally, 200 Rand monthly Grants: 870 Rand pension (50%), 200 Rand child (100%) Remittances: occasionally, Rand Expenditures Food: 120 Rand / 100 Rand / 25 Rand p.P. monthly Club fees: Rand monthly School fees: 200 Rand secondary, 1000 Rand college yearly Wages for piece jobs: occasionally, 200 Rand per job monthly Burial: occasionally, 5000 Rand / Rand contribution Lobola: occasionally, Rand New household: after marriage, Rand Initial amount of cash: randomly between 300 and 700 Rand

11 CAVES Project Meeting September 2007 ● CPM11 Declarative Model – Household Wealth Distribution

12 CAVES Project Meeting September 2007 ● CPM12 Household Economy

13 CAVES Project Meeting September 2007 ● CPM13 Declarative Model – Sexual Network People may have > 1 concurrent partners Only heterosexual relationships 2-mode network Adults from are considered sexually active Relationships form in two steps: Male sends "request" to attractive female Same age or younger Endorsement value > threshold (tag) Sibling of friend, colleague, same group, randomly Female evaluates requests and picks best male Endorsement value > threshold Max number partners not reached yet New partner better than old partners Relationships break up Better partner Randomly influenced by the number of current partners and the person’s age With marriage

14 CAVES Project Meeting September 2007 ● CPM14 Declarative Model – HIV spread Modelled on an individual basis Number of people picked to be HIV positive at initialisation Gender/age follows estimated HIV prevalence distribution from South African National HIV Survey, 2005 A person might contract HIV from an HIV-positive partner Probability of infection = * number of sexual contacts Transmission rate per contact is 0.03% Frequency of intercourse modelled as tag Higher for migrants

15 CAVES Project Meeting September 2007 ● CPM15 Declarative Model – Sexual Network

16 CAVES Project Meeting September 2007 ● CPM16 Further Experiences with Jess Find balance between expressiveness of declarative modelling in Jess and faster execution of Java Reduce number of facts in Jess Remove when no longer needed from Java DisposalPolicy / EndorsementDisposalPolicy Provide direct access to model functionality User functions instead of method calls on model object (current-tick) / (dump)

17 CAVES Project Meeting September 2007 ● CPM17 Jess Java FactbaseScourer DisposalPolicy Model FactsRules HH Person

18 CAVES Project Meeting September 2007 ● CPM18 Next steps Validation Solve household economy problem Evaluation Applying network measures Improve visualisation and data collection Discuss need with case study team


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