米国が国際開発援助(ODA)を大きく縮小するとどうなるのか?

世界的に権威ある医学の学術誌の Lancet に "Evaluating the impact of two decades of USAID interventions and projecting the effects of defunding on mortality up to 2030: a retrospective impact evaluation and forecasting analysis" と題する論文が掲載されています。要するに、現在の米国のトランプ政権が進めようとしている国際開発援助が最近20年で死亡率にどれくらいの影響を持ったかを分析し、さらに、その将来分析を行ったペーパーです。まず、引用情報は以下の通りです。共著者は15人ほどに上りますので省略しています。

• Cavalcanti, Daniella Medeiros et al. (2025) "Evaluating the impact of two decades of USAID interventions and projecting the effects of defunding on mortality up to 2030: a retrospective impact evaluation and forecasting analysis," forthcoming Lancet, Published Online June 30, 2025

続いて、Lancet のサイトから Funding を除く Summary を引用すると下の通りです。これだけでかなり長いです。

Summary
Background
The US Agency for International Development (USAID) is the largest funding agency for humanitarian and development aid worldwide. The aim of this study is to comprehensively evaluate the effect of all USAID funding on adult and child mortality over the past two decades and forecast the future effect of its defunding.
Methods
In this retrospective impact evaluation integrated with forecasting analysis, we used panel data from 133 countries and territories- including all low-income and middle-income countries (LMICs)-with USAID support ranging from none to very high. First, we used fixed-effects multivariable Poisson models with robust SEs adjusted for demographic, socioeconomic, and health-care factors to estimate the impact of USAID funding on all-age and all-cause mortality from 2001 to 2021. Second, we evaluated its effects by age-specific, sex-specific, and cause-specific groups. Third, we did several sensitivity and triangulation analyses. Lastly, we integrated the retrospective evaluation with validated dynamic microsimulation models to estimate effects up to 2030.
Findings
Higher levels of USAID funding-primarily directed toward LMICs, particularly African countries-were associated with a 15% reduction in age-standardised all-cause mortality (risk ratio [RR] 0.85, 95% CI 0.78-0.93) and a 32% reduction in under-five mortality (RR 0.68, 0.57-0.80). This finding indicates that 91 839 663 (95% CI 85 690 135-98 291 626) all-age deaths, including 30 391 980 (26 023 132-35 482 636) in children younger than 5 years, were prevented by USAID funding over the 21-year study period. USAID funding was associated with a 65% reduction (RR 0.35, 0.29-0.42) in mortality from HIV/AIDS (representing 25.5 million deaths), 51% (RR 0.49, 0.39-0.61) from malaria (8.0 million deaths), and 50% (RR 0.50, 0.40-0.62) from neglected tropical diseases (8.9 million deaths). Significant decreases were also observed in mortality from tuberculosis, nutritional deficiencies, diarrhoeal diseases, lower respiratory infections, and maternal and perinatal conditions. Forecasting models predicted that the current steep funding cuts could result in more than 14 051 750 (uncertainty interval 8 475 990-19 662 191) additional all-age deaths, including 4 537 157 (3 124 796-5 910 791) in children younger than age 5 years, by 2030.
Interpretation
USAID funding has significantly contributed to the reduction in adult and child mortality across low-income and middle-income countries over the past two decades. Our estimates show that, unless the abrupt funding cuts announced and implemented in the first half of 2025 are reversed, a staggering number of avoidable deaths could occur by 2030.

Summary をさらに短くすれば、要するに、最近20年間で米国国際開発庁(USAID)の資金援助により、under-five mortality=5歳未満児死亡率の32%減少をはじめとして、all-cause mortality=全死亡率の15%減少がもたらされています。そして、現在のトランプ政権による国際援助の大幅な資金削減により、2030年までに全年齢層の死亡者数が14百万人余り以上増加し、そのうち5歳未満の乳幼児の死亡者数は4.5百万人余りに達すると予測されています。すなわち、USAIDの資金提供は過去20年間において、低所得国および中所得国における死亡率の低下に大きく貢献してきましたし、したがって、最近トランプ政権から発表され実施された急激な資金削減により、2030年までに回避可能な死亡者数が驚くほど多くなる可能性がある、という結論です。下のグラフは、Lancet のサイトから Figure 1 Rate ratios from the fixed-effect Poisson models for the association between specific causes of death related to USAID focus areas and USAID funding per capita per year を引用しています。

「アメリカ・ファースト」を掲げて大統領選挙に勝利したトランプ米国大統領は、米国に関税の壁を張り巡らせようとしているだけではなく、こういった人道的な国際貢献も無視して政策を進めようとしています。日本の参議院選挙でもよく似たスローガンを掲げている政党や候補者がいます。外国や外国人に対する政策も十分考慮して参議院選挙で投票する必要を訴えておきたいと思います。