The most important control is evidence stance: from skeptical (~70,000 QALYs — each effect weighted by how well its study identifies causation) to credulous (~200,000 — every cited effect at face value). That gap, not the dollar figure, is the real uncertainty.

About this model

MacKenzie Scott's Yield Giving network has made over $26 billion in 2,700+ gifts since 2019 — $26.3 billion through 2025 by CNBC's year-end accounting. This page asks what that buys in quality-adjusted life-years, the unit health economists use to compare a death averted against years lived in better health.

It is a GiveWell-style model: 13 intervention archetypes, each cost-per-QALY drawn where possible from a published causal estimate (Medicaid mortality, community health centers, supportive housing, collaborative-care depression), each effect shrunk toward zero in proportion to how well its study identifies causation, and the whole thing rerun through thousands of Monte Carlo draws each time you move a slider.

I built the model with Claude; every estimate here is a model output, not a measured fact. The Python package, tests, and sources are on GitHub; this page runs a checked TypeScript implementation in the browser, reading the exported parameter file.

How it works

Each Monte Carlo draw takes the giving — each year's gifts inflated to 2026 dollars ($26.39 billion nominal ≈ $30.3 billion, so the dollars and the cost-effectiveness evidence share one price level) — allocates it across the archetypes (a Dirichlet whose centers come from Scott's own gift database — dollar amounts are disclosed for about two-thirds of the money, and each organization's dollars are split across its reported focus areas and mapped to the 13 archetypes; the undisclosed remainder is imputed from her announced year totals, scaled by each recipient's pre-gift IRS 990 revenue), assigns each a cost-per-QALY, and multiplies by two independent discounts:

The gift-size data yields one measured regularity along the way: across the 1,313 disclosed gift–revenue pairs, gift size scales with the recipient's pre-gift revenue to the power 0.41 (R² 0.37) — a 10× larger organization receives about 2.5× more money, not 10× more. That fitted elasticity, not proportionality, weights the imputation of the undisclosed gifts.

• Causal credibility — how well the effect is identified, drawn from the study's design tier: a lottery RCT (income → mortality) is trusted; an associational SNAP correlation is shrunk hard; an assumption-only bucket (arts, civic) goes to near zero. This is the evidence stance slider.
• Realization — the fraction of the studied effect a marginal unrestricted grant actually delivers.

The model also prices the same dollars at the global-health frontier. GiveWell's current impact estimates put the 2022–2024 program averages at ~$4,000 per life saved (Malaria Consortium) to ~$5,500 (AMF nets). A child death averted at ~age 1 is ~25 discounted QALYs under this model's own conventions (~65 remaining years, 3% discount, utility ~0.87), so those endpoints — inflated to 2026 dollars — become roughly $175–$241 per QALY-equivalent; I model the benchmark as loguniform $150–$260, handicapped with the same realization and credibility as Scott's portfolio (and rescaled at other discount rates) so the comparison is like-for-like. At the skeptical defaults, the frontier delivers roughly 1,500× more health per marginal dollar.

That multiple is a marginal comparison — the next dollar, not the whole portfolio. Frontier-priced opportunities are scarce: GiveWell directed $397 million in all of 2024 and moves its cost-effectiveness bar with the money it expects to raise — funding down to ~6× cash when flush, back up to 10× when projections fell. Malaria control, the deepest frontier bucket, absorbed $3.9 billion in 2024 against a $9.3 billion target, while ~610,000 people died. And the implied frontier counterfactual — ~105 million QALYs at the default settings — would mean averting ~4.2 million child deaths, most of a full year of the world's under-5 deaths; no amount of money buys that at bed-net prices. Redeploying the full $30 billion would ride up the marginal-cost curve — to a few hundred times rather than ~1,500×, at my guess — softer in magnitude, same in direction. The floor is direct cash, the one option with effectively unbounded capacity, which GiveWell now scores at 3–4× its own historic benchmark: in health-only terms, somewhere under 50–100×.

What this doesn't capture

A QALY is a health metric. Most of Scott's giving targets economic mobility, education, and equity, whose value is largely non-health — income, opportunity, rights, wellbeing. The model therefore understates her total social impact; it answers one specific question. The largest dollar buckets (equity & justice at ~22%, education at ~18%) contribute little health precisely because no credible study ties those grants to QALYs, not because the giving lacks value.

Key sources

• Sommers (2017), AJHE 3(3) — Medicaid cost per life saved $327k–$867k in 2007 dollars, CPI-U inflated here to $529k–$1.40M; mortality effect corroborated by Miller, Johnson & Wherry (2021), QJE.
• Bailey & Goodman-Bacon (2015), AER — community health centers at ~$54k per life-year (2012 dollars), ~$79k in 2026 dollars, converted to $/QALY with the model's utility draw.
• Holtgrave et al. (2013), AIDS and Behavior — Housing & Health intervention $62,493/QALY (HIV-positive unstably-housed cohort, stated in 2005 dollars; ~$107k in 2026 dollars); NASEM (2018) for the mixed-evidence assessment of supportive housing.
• Collaborative-care depression reviews (Community Guide, 2008 dollars: $17k–$39k; van Steenbergen-Weijenburg 2010: $21.5k–$49.5k, unnormalized) — roughly $26k–$77k in 2026 dollars.
• Cesarini et al. (2016), QJE — lottery evidence of a ~null causal income→mortality effect.
• HHS ASPE (2026), Table 3 — value per QALY, $726k central at a 3% discount rate in constant 2025 dollars (~$756k in May-2026 dollars), used for the benefit/cost ratio.
• GiveWell current impact estimates — 2022–2024 lives-saved program averages converted here to $150–$260 per QALY-equivalent.
• Yield Giving gift database — 2,711 gifts with dollar amounts disclosed for about two-thirds of the $26.39B; org-reported focus areas drive the allocation split (area-to-archetype mapping); undisclosed amounts imputed from year totals in proportion to pre-gift IRS 990 revenue, elasticity fit on the disclosed gifts.

Full annotated bibliography, parameter file, and the tested Python package: github.com/MaxGhenis/mackenzie-scott-qaly.