On 2025-02-12 19:59:20, user Aron Troen wrote:
Review Part II
Methodological shortcomings<br />
Study population and period: The population demographics used as the denominator of per capita caloric requirement rely on census data from 2017 and UN OCHA reports on movement and displacement of the population between Gaza governates during the war. The study states that no adjustments were made for out-migration or excess deaths. However, approximately 150,000 people left the Gaza strip from the beginning of the war until the Rafah crossing was closed in May. When added to casualties and a natural death rate of ~5500 people per year, this means that the population denominator used to calculate the food supply in Kcal per person-day (Figure 4) was overestimated by ~ 200,000 people, which would result in the underestimation of the food supply by approximately 10%.
The authors acknowledge the limitation that “There remains considerable uncertainty about our population denominators in the north, and even moderate error in these would have affected our Kcal per capita estimates. Gaza’s population has probably decreased due to high mortality and out-migration…”. Nevertheless, they shrug off this limitation by asserting that “…we expect this to have only marginally affected our estimates.” without explaining why.
Data on truck deliveries
The comparison between UN and Israeli shipping data is superficial and inadequate for supporting the decision to dismiss and exclude the data from the analysis. The authors fail to discuss the literature, of which they surely must be aware, which addresses the high-profile controversy over the number of trucks supplying aid to Gaza and the discrepancies between the UN and COGAT data, and which notes the under-reporting of private sector food shipments by the UN (see for example, Rosen, Bruce and Nitzan, Dorit, Humanitarian Food Aid for Gaza: Making Sense of Recent Data (June 02, 2024). Available at http://dx.doi.org/10.2139/ssrn.4851635) "http://dx.doi.org/10.2139/ssrn.4851635)") .
Although the authors note the "large discrepancy between UN and Israeli government data" on the entrance of goods into Gaza, they erroneously assert that UNRWA monitored the composition of “ALL trucks” crossing into Gaza, despite the partial coverage of non-UN food consignments, and despite disclaimers published by UNRWA and recorded by the authors, that the data from May-August are incomplete. The authors make little effort to help the reader understand the reason for the discrepancy nor to explain how they reached the conclusion that UNRWA's dataset "appeared highly complete and well-curated, but may be biased by systematic under- or over-reporting unknown to us". Instead of making a serious effort to include COGAT data to improve the accuracy of their simulation, they perform a perfunctory comparison of the UN and COGAT data and justify the summary dismissal of the Israeli registry, using the categorical listing of truck weight registered by COGAT as “evidence of digit heaping or crude approximation”. This is a peculiar choice, given the importance of the COGAT dataset, which is included in the June IPC report and in a working paper that the authors cite that analyzes the caloric content of food supplied to Gaza, including private sector shipments that are missing from the UN data (now published at https://ijhpr.biomedcentral.com/articles/10.1186/s13584-025-00668-6) "https://ijhpr.biomedcentral.com/articles/10.1186/s13584-025-00668-6)") . An alternative choice might have been to simulate the weight and contents of the COGAT data like the authors did for incomplete WFP data, or to perform a sensitivity analysis and compare how caloric supply estimates might differ based on the data and assumptions used.
Instead, the study implies that the discrepancy has to do more with weight of aid reported rather than the number of trucks. However, significant gaps are also evident in the number of trucks reported. For example, in February, UNRWA reported 1,857 trucks carrying food while COGAT's figure is 15% higher (2,117). In January the gap is equally large, with COGAT's number of trucks 13% higher than UNRWA's (3,364 and 2,990 respectively). According to COGAT, between January and May 2024, "as a result of the UN’s partial counting… there are 3,406 trucks missing from their Kerem Shalom data and 2,198 trucks missing from their Nitzana/Rafah data." ( https://govextra.gov.il/media/dtmhzmtn/discrepancies-in-un-aid-to-gaza-data-2.pdf) "https://govextra.gov.il/media/dtmhzmtn/discrepancies-in-un-aid-to-gaza-data-2.pdf)") . Furthermore, the period analyzed covers several unexplained changes in UNRWA's dashboard ( https://honestreporting.com/how-unrwa-covers-up-its-faulty-gaza-food-data/) "https://honestreporting.com/how-unrwa-covers-up-its-faulty-gaza-food-data/)") , apparently following data-driven criticism about its methodology and lack of transparency on social media ( https://x.com/AviBittMD/status/1780052840930578499) "https://x.com/AviBittMD/status/1780052840930578499)") . According to a FEWS NET report, "on September 8… UNRWA’s dashboard was updated with additional supply data for August, as well as for previous months, including commercial truck entries as reported to UNRWA." UNRWA has not disclosed where the new data on commercial trucks came from or how far back the data update had gone.
The subsequent calculation of caloric availability includes a mix of registered and simulated data, in which the simulation parameters extremely underestimate the caloric supply. The model derives the simulated distribution of estimated Kcal per truck as described in the methods and shown in supplementary figure A1: “We reconstructed the number of these trucks over time based on published information and data shared by WFP . As no data on content were available, we simulated their caloric equivalent by repeatedly sampling from the empirical distribution of calories per truck obtained from the UNRWA dataset.“ There are several problems with this approach. First, it is unclear which specific truck data “shared by WFP” were used for this simulation, and whether they are publicly available. This should be clearly indicated in the uploaded github data files. Moreover, the WFP records the contents of their shipments. Why were their contents omitted in this case? Presenting summary tables in the article would help the orient the reader to the source data for the truck counts used, distinguishing between simulated or assumed and actual contents. An implicit assumption underlying the simulation of WFP contents according to estimated distribution of calories by UNRWA trucks, is that the contents of UNRWA and WFP shipments are the same. This needs to be documented or the assumption should be made explicit. Given that the study appears to significantly underestimate the weight of the UNRWA pallets, the procedure used would be expected to propagate biased estimates lower than the actual weights to the WFP data as well.
The most critical problem in the model is with the ASSUMED weights that the authors assign to the consignments. They assume mean pallet weights to be 637.5 kg per pallet, with a minimum to maximum weight of 510-765 kg per pallet (gaza_food_data.xlsx, general tab), based on citations 23, 30 and 31. Citation 23 does not provide supporting data and refers to IPC reports in general. Citations 30 and 31 are standard operating procedures for the Egyptian Red Crescent (ERC) from October and November 2023, which REQUIRE an 18% higher palletization weight of 750 kg. However, even this value is considerably lower than UN aid REQUIREMENTS that specify pallet weights for wheat flour (1125-1200 kg/pallet), sugar (1200 kg/pallet), chickpeas 1200 kg/pallet), red lentils (1200 kg/pallet), rice (1200 kg/pallet), SF oil (910-1213 kg/pallet) or milk (655 kg/pallet) (UNRWA Special Shipping Instructions for Shipments by Sea Air and Land – April 2024 - page 6; https://unrwa.org/sites/default/files/emergency_gaza_2023-_rfq-pskh-42-24-the_provision_of_man_trucks_for_gfo-tender_doc.pdf) "https://unrwa.org/sites/default/files/emergency_gaza_2023-_rfq-pskh-42-24-the_provision_of_man_trucks_for_gfo-tender_doc.pdf)") . Examination of “dataset 20240911_Commodities Received.xlsx” reveals that consignments attributed to ERC alone or with other agencies (including UNRWA) account for only 90,009 of the total of 531,175 food line items (17%) and 8085 of the total of 22,833 mixed line items (35%). Therefore, even if the mean value of 637.5 kg/pallet were correct for the ERC-associated consignments, the weights assigned to the foods supplied are unreasonably low, giving an extreme underestimation of the calories supplied.
This unreasonably low distribution of the estimated Kcal per truck can be seen in the simulated truck weights. The histogram in Appendix figure A1 shows a distribution that is heavily skewed to the left with the vast majority of trucks carrying less than 50 Million Kcal and perhaps a third carrying less than 25 Million Kcal. The simulated lower end of the distribution, which begins with 600 trucks carrying zero Kcal/truck, is highly unlikely to be accurate. Even if one takes the assumed mean weight per truck assigned by the researchers as 14,500 kg, multiplying by the calorie content of wheat flour (3,640 Kcal/kg) would give a mean calorie content per truck of 52.8 M Kcal. Even if a lower calorie food calorie density of circa 3200 Kcal/kg were used, based on visual inspection of Figure 3A (Kcal/kg food consignments between Oct 21 2023 – May 4 2024), the assumed mean caloric content of the food trucks should be 46.4 Million Kcal. These values, are hard to reconcile with the histogram, even if the assumed and simulated truck weights in the model are true. Thus, the validity of the model assumptions and their potential for propagating error and uncertainty in the results should be carefully revisited.
Data on other food sources
Estimates of the available existing food supply before the war combine the household stocks of humanitarian food aid, data provided to the researchers by UNRWA giving the exact stocks in UNRWA warehouses and the range of minimum-maximum capacity of WFP warehouses before the war; estimates of existing private stores, and of agriculture and livestock production, discounted for gradual depletion and destruction during the war’s early months. The model does not account for potential Hamas stockpiles ( https://www.nytimes.com/2023/10/27/world/middleeast/palestine-gazans-hamas-food.html) "https://www.nytimes.com/2023/10/27/world/middleeast/palestine-gazans-hamas-food.html)") .
The spreadsheet “gaza_food_data.xlsx” tab “warehouses” lists total UNRWA and WFP warehouse capacity before the war as a range with a minimum to maximum capacity of 7,900-21,479 MT or 28.7 – 78.1 billion Kcal, whereas presumably, the “exact” contents of the food in UNRWA warehouses are those data listing a total of 38.3 billion Kcal of food in tab “unrwa_stocks”. No further information is provided to ascertain that the data given to the researchers by UNRWA and WFP is complete and accurate.
Existing private stores/Caloric balance and consumption: The text describes the assumptions used in estimating the existing stores and their depletion during the war. The text defines model parameters (eg. I0, I0,m, etc.) but does not spell out the full model equation. Doing so would help the readers better understand the explicit logic of the simulation. <br />
The model discounts agriculture and livestock production using estimates of the rate and extent of damage to agricultural infrastructure citing UNOSTAT remote sensing data published by FAO (references 11, 40-42). The validity of estimates derived from image analysis depends heavily on the control conditions selected for a reference and on the quality of validation and calibration in the field. The percent damage arrived at by automated image analysis algorithms, depends on the selected reference conditions, whose rationale and validity are not given. Field validation is impossible in a war zone which is why the cited reports carry important disclaimers such as: ”This assessment has been conducted based on available satellite imagery, ancillary data and remote sensing analysis for the period 7 October - 31 December 2023 without field validation. Land cover data from 2021 was used as baseline data due to limited availability for data collection in the area of interest and time constraints related to the nature of the report.“ ( https://openknowledge.fao.org/server/api/core/bitstreams/f2ad2f59-0c29-472e-978b-54cef347c642/content) "https://openknowledge.fao.org/server/api/core/bitstreams/f2ad2f59-0c29-472e-978b-54cef347c642/content)") . The limitations of these estimates used in the model should be acknowledged.
Estimating Baseline and Recommended per-capita caloric intake
The per-capita caloric intake for emergency-affected populations is given by the WHO guide and is stratified by age and sex. Given the age and sex distribution of the population of Gaza (gaza_food_data.xlsx, tab prop_age_sex), the mean daily per capita calorie requirement for the population is 2,065 Kcal/person-day. This threshold shown in yellow in Figure 4, is the appropriate criterion for evaluating the adequacy of the food supplied by the humanitarian food cluster. <br />
However, the researchers go beyond this consensus humanitarian requirement, and derive a much higher Gaza-specific estimate “I0“ for the population intake at baseline. The baseline value of I0 appears to be just under 2,800 Kcal per person-day according to figure 4 (blue line value on October 7th, 2023). The paper does not give the baseline value “I0“ explicitly. However, it is nearly identical to the weighted average caloric intake (2,837 Kcal/person-day) observed in a population of obese older Gazan adults (mean age 57, weighted mean BMI 31.4) with a high prevalence of noncommunicable diseases, in a survey conducted during the COVID pandemic between March and July 2020, which was used to impute the daily intake of the overall population. The weighted intake and BMI may be calculated based on the data provided in the gaza_food_data.xlsx spreadsheet, tab prop_age_sex. The estimated pre-war intake, is roughly 33% higher than the humanitarian requirement, or “recommended daily intake”. The model derives the weekly available per person food supply, by subtracting this pre-war intake estimate, from the estimated weekly available daily per-capita food supply (from the sum of private stores and warehouses, agriculture and delivered food-aid, discounted for reported consumption and damage). The model makes the questionable assumption that the emergency-affected population would continue to consume the same amount of food that it did during the war, as it did before the war. Even before examining the validity of the method used to derive “I0“, this assumption forces the model to deplete the available food supply significantly more rapidly (about 33% sooner) than if the recommended humanitarian food requirement were used to simulate the adequacy of the available food supply.
The logic behind the method of imputation to the whole population is not clearly explained (“we sampled random values from each age-sex stratum distribution…” Appendix A, Figure A2). <br />
Supplementary figure A2, entitled “Baseline adult caloric intake” shows simulated untransformed and log-transformed, age and sex specific distributions of energy intake, from Abu Hamad et al., J Hum Hypertens 2023. That reference describes a health survey conducted in Gaza between March and July 2020 among adults aged 40 and older, and using the semi-quantitative Food Frequency Questionnaire for Palestinian Populations which was developed by Hamdan et al., in a population of Palestinian women in Hebron, and published in Public Health Nutrition 17(11) in 2013. While such survey tools may be useful for epidemiological studies, they are intended to classify populations into categories of relative nutritional intake, rather than for deriving valid absolute individual nutrient intakes. In the case of the specific instrument used, Hamdan et al. write that studies like theirs “can be considered a calibration and correlation rather than a validation procedure”. The correlation that they obtained in that study between three repeat 24 hr food recall questionnaires and the semi quantitative FFQ was 0.601 and was not statistically significant (in other words the FFQ gives a similar but poorly concordant result to the reference standard). Moreover, it is doubtful, if the high average food intake of an obese, older and unhealthy population (which was obtained during a health crisis that increased sedentary behavior due to social distancing and isolation), provides a sound basis for imputing routine intakes for a population that is predominantly younger (82% of Gaza’s population are below age 40 – see gaza_food_data.xlsx, tab prop_age_sex), healthier, and not affected by a pandemic. It would be helpful if the researchers clarified these limitations and presented the age-and sex stratified per-person daily caloric derived intake and compared it with the consensus humanitarian requirements.