Charitable impact varies enormously between different interventions

MacAskill's opening argument is that people often assume charities occupy a roughly similar band of effectiveness, when in reality some documented interventions achieve outcomes many times more cost-effective than others addressing similar problems, simply because certain approaches are backed by stronger evidence, target more tractable problems, or reach more people per dollar spent. Choosing between charities without checking evidence is therefore a much higher-stakes decision than it feels like.

He illustrates this with comparisons across global health and poverty interventions, where some programs have been rigorously studied through controlled trials and shown to reliably produce specific, measurable benefits, while others with equally appealing marketing have little independent evidence supporting their claimed impact.

The practical implication is that picking a charity based on emotional resonance or a compelling story, without checking effectiveness evidence, risks doing dramatically less good than the same donation directed elsewhere. Takeaway: because effectiveness varies so widely between charities, checking evidence before donating matters as much as the decision to donate at all.