Rights statement: This is an Accepted Manuscript of an article published by Taylor & Francis in Journal of Human Trafficking on 06/09/2019, available online: https://www.tandfonline.com/doi/full/10.1080/23322705.2019.1660952
Accepted author manuscript, 419 KB, PDF document
Available under license: CC BY-NC: Creative Commons Attribution-NonCommercial 4.0 International License
Final published version
Research output: Contribution to Journal/Magazine › Journal article › peer-review
Research output: Contribution to Journal/Magazine › Journal article › peer-review
}
TY - JOUR
T1 - On the Unreliability of Multiple Systems Estimation for Estimating the Number of Potential Victims of Modern Slavery in the UK
AU - Whitehead, J.
AU - Jackson, James
AU - Balch, A.
AU - Francis, B.
N1 - This is an Accepted Manuscript of an article published by Taylor & Francis in Journal of Human Trafficking on 06/09/2019, available online: https://www.tandfonline.com/doi/full/10.1080/23322705.2019.1660952
PY - 2021/1/2
Y1 - 2021/1/2
N2 - Accurate records of victims of modern slavery identified by various agencies allow investigators to compare different jurisdictions, track fluctuations in prevalence over time and evaluate preventative interventions. As well as enumerating those victims known to agencies, it would be desirable to know how many are working undetected under conditions of modern slavery and thus deduce the total number involved. To estimate the number of undetected potential victims of modern slavery in the UK, Bales, Hesketh and Silverman applied the method of Multiple Systems Estimation. Their approach involves fitting a statistical model to data listing victims detected by different agencies. In doing so, (a) they assume that various terms in the model are equal to 1, and (b) they only include terms not assumed to be 1 if they achieve statistical significance. In this paper, simulated datasets with known properties are used to show that if (a) is valid then (b) leads to substantial overstatement of the reliability of the estimates computed, and that if (a) is not valid then the estimation procedure is totally unsound. We conclude that Multiple Systems Estimation is not a suitable method for estimating numbers of potential victims of modern slavery.
AB - Accurate records of victims of modern slavery identified by various agencies allow investigators to compare different jurisdictions, track fluctuations in prevalence over time and evaluate preventative interventions. As well as enumerating those victims known to agencies, it would be desirable to know how many are working undetected under conditions of modern slavery and thus deduce the total number involved. To estimate the number of undetected potential victims of modern slavery in the UK, Bales, Hesketh and Silverman applied the method of Multiple Systems Estimation. Their approach involves fitting a statistical model to data listing victims detected by different agencies. In doing so, (a) they assume that various terms in the model are equal to 1, and (b) they only include terms not assumed to be 1 if they achieve statistical significance. In this paper, simulated datasets with known properties are used to show that if (a) is valid then (b) leads to substantial overstatement of the reliability of the estimates computed, and that if (a) is not valid then the estimation procedure is totally unsound. We conclude that Multiple Systems Estimation is not a suitable method for estimating numbers of potential victims of modern slavery.
KW - Modern Slavery
KW - multiple systems estimation
KW - estimating victims
KW - capture recapture
KW - human trafficking
U2 - 10.1080/23322705.2019.1660952
DO - 10.1080/23322705.2019.1660952
M3 - Journal article
VL - 7
SP - 1
EP - 13
JO - Journal of Human Trafficking
JF - Journal of Human Trafficking
SN - 2332-2705
IS - 1
ER -