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Educational Research - the Ethics and Aesthetics of Statistics

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7 To Frame <strong>the</strong> Unframable: Quantifying Irregular Migrants’ Presence 109<br />

Appendix 1: Methods for Stock Estimates<br />

Approach Data sources Method Estimation technique Main idea <strong>of</strong> calculation<br />

Direct<br />

approaches<br />

Based on immigration<br />

enforcement data<br />

Based on administrative<br />

statistics<br />

Multiplier methods Simple Multiplier Estimation <strong>of</strong> total with a simple multiplier<br />

based on derived or estimated ratio <strong>of</strong> ‘dark<br />

field’ vs. ‘clear field’<br />

Methods <strong>of</strong><br />

self-identification<br />

Capture-recapture/ Repeated<br />

capture<br />

Estimation based on probabilistic function<br />

derived from multiple recaptures <strong>of</strong><br />

individuals in sample<br />

Matching <strong>of</strong> registers Estimation based on implied non-registration in<br />

two or more individually matched registers<br />

R<strong>and</strong>om effect mixed<br />

modelling approach<br />

Evidence based on<br />

regularisation data<br />

Using data on status<br />

adjustments over time<br />

Estimation using statistical regression model<br />

assuming comparable apprehension rates <strong>of</strong><br />

legal/illegal residents with statistical<br />

adjustment for r<strong>and</strong>om effects<br />

Inferences on <strong>the</strong> size <strong>and</strong> composition <strong>of</strong><br />

irregular migrant stock prior to regularisation<br />

from data on applications for <strong>and</strong> grants <strong>of</strong><br />

regularisations<br />

Inferences derived from data on changes in<br />

residence status after a period <strong>of</strong> irregular<br />

residence<br />

Based on surveys Survey methods Direct survey methods Reconstruction <strong>of</strong> a "r<strong>and</strong>om sample" <strong>of</strong><br />

regular <strong>and</strong> irregular migrants through a<br />

re-weighting <strong>of</strong> <strong>the</strong> probability <strong>of</strong> contacts<br />

Snowball sampling methods Estimation using chain referral methods to<br />

obtain a sample <strong>of</strong> persons not registered vs.<br />

persons registered

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