Paper accepted to Demographic Research

Got the news recently that a paper by Jakub Bijak, Jason Hilton and myself has been accepted for publication in Demographic Research, an open-access journal for demography and population sciences.  We’re very pleased to see our work accepted, particularly as we’re offering up a relatively unconventional approach.

We’ve just sent in the final version for editing/formatting, so it won’t be online for a little while.  In the meantime here’s the abstract:

Reforging the Wedding Ring:  Exploring a Semi-Artificial Model of Population for the United Kingdom with Gaussian Process Emulators

Background We extend the ‘Wedding Ring’ agent-based model of marriage formation to include some empirical information on the natural population change for the United Kingdom together with behavioural explanations that drive the observed nuptiality trends.

Objective  We propose a method to  explore statistical properties of agent-based  demographic models.  By coupling rule-based explanations driving the agent-based model with observed data we wish to bring agent-based modelling and demographic analysis closer together.  

Methods We present a Semi-Artificial Model of Population, which aims to bridge demographic micro-simulation and agent-based traditions.  We then utilise a Gaussian process emulator  – a statistical model of the base model – to analyse the impact of selected model parameters on two key model outputs: population size and share of married  agents.  A sensitivity analysis is attempted, aiming to assess the relative importance of different inputs.

Results The resulting multi-state model of population dynamics has enhanced predictive capacity as compared to the original specification of the Wedding Ring, but there are some trade-offs between the outputs  considered.   The sensitivity analysis  allows  identification of  the most important parameters in the modelled marriage formation process.  

Conclusions  The proposed methods allow for generating coherent, multi-level agent-based scenarios aligned with  some aspects of empirical demographic reality.  Emulators permit a statistical analysis of their properties and help select plausible parameter values.

Comments Given non-linearities in agent-based models such as the Wedding Ring, and the presence of feedback loops, the uncertainty of the model may not be directly computable by using traditional statistical methods.  The use of statistical emulators offers a way forward.

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