Study challenges reliability of widely cited Gaza mortality survey in The Lancet Global Health

A newly published correspondence in The Lancet Global Health challenges the reliability of a widely cited Gaza Mortality Survey. Based on a reanalysis of the survey's publicly released data, the authors identify interviewer-level anomalies, departures from the stated sampling methodology, and inconsistencies with external demographic data, arguing that these issues raise significant concerns about the survey's representativeness and the validity of its estimates of conflict-related deaths in Gaza.

Professor Emeritus Sergio DellaPergola, one of the world's leading demographers and a senior scholar at the Hebrew University of Jerusalem, has published a correspondence in The Lancet Global Health questioning the reliability of a widely cited Gaza Mortality Survey that estimated approximately 75,200 violent deaths during the Israel–Hamas conflict. Conducted together with independent researcher Mark Zlochin, the analysis identifies methodological concerns that, according to the authors, call into question the survey's claim of population representativeness – hence the estimates about the number of victims.

DellaPergola and Zlochin re-examined the publicly available survey microdata and supplementary materials, identifying substantial interviewer-level differences and apparent departures from the survey's declared sampling procedures. Their correspondence argues that these issues may undermine the validity of extrapolating the survey's findings to the broader Gaza population.

Among the key findings, the researchers note that one interviewer team recorded roughly one-quarter of all reported violent deaths while surveying only a small fraction of the sampled households. The correspondence also identifies demographic anomalies among certain interviewer teams and presents evidence suggesting that the survey's quality-control mechanisms failed to detect significant irregularities during data collection.

"Population-level mortality estimates are only as reliable as the representativeness of the underlying sample," said DellaPergola. "Our analysis raises important questions regarding whether the survey achieved the level of representativeness necessary to support its national mortality estimates."

The authors further point to GPS-based evidence indicating deviations from the survey's stated sampling protocol. Different sampling areas, instead of being separated, actually overlapped. Interviewers covered only small portions of the areas allocated to them, thus missing variability due to population dispersal over the territory. There were serious doubts about possible double counting of deaths, due to the split of reporting families under the hardness of the war situation. Causes of death were not reported, although the information was collected in the survey. The critique also highlights significant discrepancies between the survey's estimates of imprisoned Gazans and independently reported detention figures. Together, they argue, these findings warrant caution in interpreting the study's mortality estimates.

Widely recognized for his pioneering work in demography and population studies, DellaPergola has spent decades analyzing population trends in Israel, the Jewish world, and the Middle East. He significantly contributed to the study of poorly defined populations – namely Jewish communities throughout the world – and developed methods for data collection and critical evaluation. The DellaPergola-Zlochin publication contributes to an ongoing scientific debate regarding the methodologies used to estimate casualties in conflict zones.