Compara mètodes

	Residual Method for Unauthorized Population	Network Scale-Up Method
Camp	Migration Studies	Migration Studies
Família	Process / pipeline	Process / pipeline
Any d'origen	1987	1998
Autor original	Robert Warren and Jeffrey S. Passel	Peter Killworth, Christopher McCarty, H. Russell Bernard, and colleagues
Tipus	Demographic-accounting estimation pipeline for unauthorized population	Indirect network-based size-estimation pipeline for hidden populations
Font seminal	Warren, R., & Passel, J. S. (1987). A Count of the Uncountable: Estimates of Undocumented Aliens Counted in the 1980 United States Census. Demography, 24(3), 375-393.	Bernard, H. R., Hallett, T., Iovita, A., Johnsen, E. C., Lyerla, R., McCarty, C., Mahy, M., Salganik, M. J., & Stroup, S. (2010). Counting Hard-to-Count Populations: The Network Scale-Up Method for Public Health. Sexually Transmitted Infections, 86(Suppl 2), ii11-ii15.
Àlies	Demographic Residual Method, Warren-Passel Residual Method, Census-Minus-Legal Residual, Unauthorized Foreign-Born Residual	NSUM, Scale-Up Method, Aggregate Relational Data Method, Known-Population Network Estimation
Relacionats	3	3
Resum	The residual method estimates the size of the unauthorized migrant population by subtraction: it takes the total foreign-born population counted in a census or large survey and removes the part that can be accounted for as legally resident, treating whatever remains as the unauthorized residual. Robert Warren and Jeffrey Passel introduced and validated the approach in their landmark 1987 Demography article, which matched undocumented aliens counted in the 1980 United States census against administrative records of legal immigrants. The arithmetic is deceptively simple, but the credibility of the estimate lives entirely in the adjustments. The legally resident stock must be aged forward from admission records and reduced for those who have since died or emigrated, and the resulting residual must be inflated to account for the share of unauthorized migrants the census itself failed to count. Done carefully and computed within detailed demographic cells — by age, sex, country of birth, and period of entry — the method turns two imperfect data sources that each say nothing directly about legal status into a defensible national estimate. It remains the dominant approach used by United States statistical agencies and research centers to size the unauthorized population.	The network scale-up method (NSUM) estimates the size of a hidden population — such as undocumented migrants or members of a stigmatized group — by asking ordinary people in a general survey how many members of that population they personally know. Developed by Killworth, McCarty, Bernard, and colleagues and formalized in their 1998 Evaluation Review paper, it rests on a simple bookkeeping idea: if you know roughly how many people each respondent knows in total, and you observe how many of those acquaintances belong to the hidden group, you can scale that fraction up to the whole society. The trick to recovering the total acquaintance count is to ask about several groups whose sizes are already known — people named Michael, nurses, women who gave birth last year — and use the responses to calibrate each respondent's personal-network size. Bernard and colleagues' 2010 review brought the method into mainstream public-health surveillance and emphasized two crucial corrections: transmission bias, because people often do not know which of their acquaintances belong to a hidden group, and barrier effects, because the hidden group may be socially clustered away from typical respondents. For migration research NSUM is attractive precisely because it never requires contacting migrants directly; it infers their numbers from the social fabric of the wider population.