Archive for Syrian civil war
an upside down year [cover]
Posted in Books with tags 2024, cover, Donald Trump, Emmanuel Macron, French politics, Léon Marchand, Libé, Middle East, Monique Pélicot, New Year's Eve, Paris 2024 Olympics, political crisis, rape, sexual violence, Solidarity with Ukraine, Syrian civil war, UNiTE to End Violence against Women on December 30, 2024 by xi'an
shallow big man [jatp?]
Posted in pictures, Travel with tags bronze sculpture, CNRS, Donald Trump, EHESS, GREQAM, jatp, Khaled Dawwa, La Vieille Charité, Marseille, museum, Panier, Syria, Syrian civil war, US elections 2024, Ville de Marseille on November 5, 2024 by xi'an
how many migrants died trying to reach Europe?
Posted in Books, Kids, pictures, Statistics, Travel, University life with tags Annals of Applied Statistics, capture-recapture, death at sea, Europe, Frontex, IMS, Mediterranean Sea, migrations, refugees, Syrian civil war, United against Racism, Università di Roma Tor Vergata on February 6, 2024 by xi'an
“We estimated that about 40,000 human beings have died trying to enter the European Union, during about 5500 tragic attempts, in the period between January 1993 and March 2019.”
A paper by Alessio Farcomeni published last year in Annals of Applied Statistics [that is delivered to me by regular mail, but which I missed] about estimating the number of deaths on migration routes. I have been interested in this question for moral and statistical reasons since the beginning of the Syrian civil war and the induced massive increase in the number of people attempting to cross the Mediterranean Sea to reach Europe. Unfortunately, despite different attempts to contact governmental agencies (like the French Minister of the Interior), NGOs (like Amnesty), friends, academics (incl. a Dutch group on that very topic but with no data or data scientist), and connections (with the Italian Navy, the Tunisian government and Frontex), I could not access more than newspaper level data or highly local data that did not allow for a general picture.
“The law of large numbers guarantees consistency as long as the population size estimator is consistent and the model is well-specified.”
As it was my intention, the paper uses capture-recapture. The data is obtained from UNITED for Intercultural Action. It had recorded 4333 attempts to enter Europe that had at least one death occurring, between January 1993 and March 2019, as reported by one or several sources, like newspaper articles. Sources that are most often not independent, but rather copying one another, which is obviously problematic for the extrapolation to the unreported cases and for resorting to capture-recapture estimation. And the number of deaths per event is itself most likely inexact, since casualties are not always recovered or identified as such. Since migration routes, migrant flows, and smuggler policies keep massively changing, the homogeneity of the observations over nearly 30 years is low to inexistent, which makes invoking consistency rather inappropriate. This is also the reason why I find the approach followed by the paper too strongly model-based as for instance when relying on an Horvitz-Thompson estimator or using a GLM to link the number of deaths in one crossing and the number of sources reporting the tragedy. This fundamental difficulty in modelling or inferring from such unreliable and untrustworthy data sources and the absence of record linkage with other datasets like the entries in the border countries (e.g., Turkey) or the number of prevented crossings by the local coastguards alas make the final estimate of 40,000 deaths at sea close to impossible to calibrate from a model-free perspective. The actual figure is not only higher, but maybe considerably so. Unfortunately, the datasets that would allow linkage and recapture are unavailable or inexistent in departure countries, while arrival countries most abstain from storing data about the migrant flows and histories…
day five at ISBA 22
Posted in Mountains, pictures, Running, Statistics, Travel, University life with tags ACDC, antivaxers, Ca' Foscari University, Canada Day, conference practicals, copulas, freedom convoy, harmonic mean estimator, infinite variance estimators, ISBA 2022, J.R. Tolkien, k nearest neightbour, Leonard Cohen, linguistics, machine learning, migrants, mirror workshop, Mont Royal, Montréal, PDMP, Plateau-Mont Royal, PMCABC, raccoon, Syrian civil war, The Lord of the Rings, University of Warwick, Venezia, Westmount, Zig-Zag on July 4, 2022 by xi'an
Woke up even earlier today! Which left me time to work on switching to Leonard Cohen’s song titles for my slide frametitles this afternoon (last talk of the whole conference!), run once again to Mon(t) Royal as all pools are closed (Happy Canada Day!, except to “freedom convoy” antivaxxxers.) Which led to me meeting a raccoon by the side of the path (and moroons feeding wildlife).
Had an exciting time at the morning session, where Giacomo Zanella (formerly Warwick) talked on a mixture approach to leave-one-out predictives, with pseudo-harmonic mean representation, averaging inverse density across all observations. Better than harmonic? Some assumptions allow for finite variance, although I am missing the deep argument (in part due to Giacomo’s machine-gun delivery pace!) Then Alicia Corbella (Warwick) presented a promising entry into PDMP by proposing an automated zig-zag sampler. Pointing out on the side to Joris Bierkens’ webpage on the state-of-the-art PDMP methodology. In this approach, joint with with my other Warwick colleagues Simon Spencer and Gareth Roberts, the zig-zag sampler relies on automatic differentiation and sub-sampling and bound derivation, with “no further information on the target needed”. And finaly Chris Carmona presented a joint work with Geoff Nicholls that is merging merging cut posteriors and variational inference to create a meta posterior. Work and talk were motivated by a nice medieval linguistic problem where the latent variables impact the (convergence of the) MCMC algorithm [as in our k-nearest neighbour experience]. Interestingly using normalising [neural spline] flows. The pseudo-posterior seems to depend very much on their modularization rate η, which penalises how much one module influences the next one.
In the aft, I attended sort of by chance [due to a missing speaker in the copula session] to the end of a session on migration modelling, with a talk by Jason Hilton and Martin Hinsch focussing on the 2015’s mass exodus of Syrians through the Mediterranean, away from the joint evils of al-Hassad and ISIS. As this was a tragedy whose modelling I had vainly tried to contribute to, I was obviously captivated and frustrated (leaning of the IOM missing migrant project!) Fitting the agent-based model was actually using ABC, and most particularly our ABC-PMC!!!
My own and final session had Gareth (Warwick) presenting his recent work with Jun Yang and Kryzs Łatuszyński (Warwick) on the stereoscopic projection improvement over regular MCMC, which involves turning the target into a distribution supported by an hypersphere and hence considering a distribution with compact support and higher efficiency. Kryzs had explained the principle while driving back from Gregynog two months ago. The idea is somewhat similar to our origaMCMC, which I presented at MCqMC 2016 in Stanford (and never completed), except our projection was inside a ball. Looking forward the adaptive version, in the making!
And to conclude this subjective journal from the ISBA conference, borrowing this title by (Westmount born) Leonard Cohen, “Hey, that’s not a way to say goodbye”… To paraphrase Bilbo Baggins, I have not interacted with at least half the participants half as much as I would have liked. But this was still a reunion, albeit in the new Normal. Hopefully, the conference will not have induced a massive COVID cluster on top of numerous scientific and social exchanges! The following days will tell. Congrats to the ISBA 2022 organisers for achieving a most successful event in these times of uncertainty. And looking forward the 2024 next edition in Ca’Foscari, Venezia!!!
Rapatriement des enfants et de leurs mères détenus dans des camps en Syrie
Posted in Kids with tags Daesh, French politics, Human Rights, Kurdistan, Ligue des Droits de l'Homme, Syrian civil war, tribune on June 27, 2021 by xi'an
