Wealth redistribution policies to mitigate the impact of development assistance defunding: a retrospective evaluation and forecasting analysis up to 2030

​​​Background. The ongoing decline in funding for humanitarian and development assistance stands in stark contrast to the global rise in wealth concentration and widening socioeconomic inequalities. This study aimed to assess whether the implementation of ​​ wealth-redistribution policies proposed in recent high-level international agreements to support development could mitigate the health impact of the current Official Development Assistance (ODA) defunding crisis. ​​ Methods. We conducted an integrated retrospective and forecasting analysis using longitudinal panel data from 59 low-income and ​​lower-middle-income countries (LLMICs). First, we estimated the association between per-capita ODA and mortality outcomes from 2002 to 2021 using two-way fixed-effects multivariable Poisson regression models with robust standard errors, adjusting for key demographic, socioeconomic, and health-system covariates. We performed extensive sensitivity and triangulation analyses to assess the robustness and plausibility of the findings. We then evaluated ten wealth-redistribution policies with validated country-level microsimulation models to forecast mortality under alternative wealth redistribution scenarios versus defunding through 2030. ​​​Findings. Higher ODA funding levels were associated with a 24% reduction in age-standardised all-cause mortality (rate ratio [RR]:0.76;95%CI:0.67-0.87) and a 33% reduction in under-five mortality (RR:0.67;95%CI:0.50-0.89). ​​Forecasting analyses showed that under the current ODA funding reductions in LLMICs, all ten wealth redistribution policies were associated with millions of averted deaths by 2030​:​ in all ages, from 6,591,984 (95%UI:4,884,075–8,374,138) for a 3% Crypto Tax of the top 10,000 holders to 29,509,934 (95%UI:20,273,842–38,603,961) for a 3% wealth tax on ultra-high-net-worth individuals​;​ in children under-five, from 1,312,912 (95%UI:802,926–1,785,121) to 3,464,607 (95%UI:1,235,930–5,609,331), respectively. Interpretation. The implementation of wealth-redistribution policies proposed in recent high-level international agreements could mitigate the health consequences of the current ODA defunding crisis, avert millions of deaths, and support the achievement of the Sustainable Development Goals.