Ulf Christian Ewert, Mathias Roehl and Adelinde Uhrmacher

Max Planck Institute for Demographic ResearchDoberaner Str. 114D-18057 RostockGermany

Demographic and economic consequences of mortality crises in pre-modern Europe

Does agent-based simulation help to gain new insights into the course of recovery-from-desaster processes?

University of Rostock, Department of Computer Science, Research Group Modelling and SimulationAlbert-Einstein-Straße 21D-18059 RostockGermany

Historical representation of the topic

„Die erschreckliche Wasser-Fluth.” [The horrible storm tide], taken from Happel, „Die größten Denkwürdigkeiten der Welt”, 1683.

Definition Mortality crisis is a decline of populationthat is mortality induced, excessive, rapid, has presumably negative demographic and economic consequences

Modern scientific representation

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TIME (Months)

BIRTHS

DEATHS

BIRTHS (slow recovery)

BIRTHS (stagnation)

Causes of mortality

crises � What are causes of mortality crises?

epidemics, famines, natural desasters, wars

mortality crisis is a structural element of the history of pre-modern Europe!

� Selected example: The Low Countries during late Middle Ages

bubonic plagues (1348, 1400) famines (1315/17; 1407/08; 1437/40) heavy storm tides (1362; 1436) casualities of war (“the Hundred Year’s War”) local desasters (fire in Lille, 1400)

Consequences of mortality crises

� What sort of consequences do we expect?

demographic consequences: sharp fertility decline (increase in fertility) distortion of age and sex ratios

economic consequences: paralysis of local markets sharp increase in food prices increase of nominal wages (per capita income)

cultural consequences: superstitions anticipation of apocalypse

Causal model

� Causal interactions

DESASTER DEMOGRAPHY

ECONOMY

first-order-effects

second-order-effects

second-order-effects

first-order-effects

crisis management

precautionary measures

precautionary measures

crisismanagement

having grain in stock

closing the town;

construction of dikes;

defending the town

attracting in-migration

abolishing marriage regulations

intervening in market processes

starting job-creation programmes

Focus of the analysis

� What is the focus when studying mortality crises?

analysis of the course of the recovery process

assessment of effects of distorted age and sex ratios

judgement of the role of crisis management in overcoming negative consequences of the crisis

� Why can the study of mortality crises be useful for today’s Demography?

comparison to consequences of current desasters in developing countries

Appropriateness of agent-based modelling

� Why agent-based modelling is appropriate to study such crises?

trade-off between historical accuracy and structural simplicity

agent-based modelling enables to distinguish several sorts of reaction patterns to the crisis!

� Example: Medieval and Early Modern Towns

craftsmen: nobody wants to buy their products, marriage plans will be delayed

labourers: real wages are raising, marriage plans can be executed

Actors, Systems, Interactions

� Actors

merchants craftsmen labourers local authority

� Systems grain market consumer good market labour market marriage market public opinion environment of town

represents demographic and economic developments outside of the town

represents the supply of goods to the town

import and sell grain seek to maximize their profit have to find marriage partners

produce and sell goods seek to maximize their profit have to find marriage partners supply labour to craftsmen seek to maxime their savings have to find marriage partners seeks to keep order intervenes in market processes changes market regulations changes marriage norms implements measures to attract in-migration

represents the supply of food to the town

represents the working relations in the town stratified segmentation of actors

strongly regulated by norms emerges from actors’ satisfaction represents degree of order

� Modelling Actors, Systems & Interactions

Modelling

approach framework for modelling & simulation separation between institutions and individuals acting by communication

� Modelling institutions

Model

macro level view economic, mathematical models

�Modelling the population – composition actor groups decision processes

Model

� Modelling the population – classification utility-based decision making (quantitative) planning (qualitative, symbolic)

Model

� A deliberative agent : The Local Authority resource bounded BDI-architecture

Agent

architecture

� A decision situation current situation: all actor groups are unsatisfied supply of grain and labour is too low in the town supply of consumer goods is sufficient Local Authority has little money and much grain available

selected goals: all actor groups should be satisfied sufficient supply of labour, grain and goods Local Authority has still some money available

Sample scenario

� Developed intentions

Deliberation result

� Where do we stand?

State-of-the-art

agents (local authority): specification of beliefs, desires, plan operators integration of general planning system (GraphPlan) planning experiments: exploring the interplay between beliefs, desires, plan operators

actors (merchants, craftsmen, labourers): modelling of utility-based decision rules but not yet tested

institutions (markets, public opinion, environment of the town): modelling of general structure but not yet tested

� Implementation in JAMES

sound system theoretic foundation (DEVS)

a J ava-based A gent M odelling E nvironment for S imulation

clear separation between model & simulation modular hierarchical composition parallel, distributed execution variable structure models

Simulation

� Does agent-based simulation help to gain new insights into the course of recovery-from-desaster processes?

Prospects of the

model � What are future prospects of the model?

reproduction of recovery-from-desaster processes on the basis of micro-macro-level interactions measurement of the relative impact of demographic and economic distortions

comparison of recovery processes due to different causes and characteristics of the crisis comparison of scenarios with various degrees of intervention by the local authority

simulation of sequential desasters with learning agents (local authority)