The ten percent tithe
Rees Calder · 18 April 2026 · 6 min read
Religious traditions have been asking people to give ten percent of their income for roughly three thousand years. The Hebrew Bible codified the ma'aser in Numbers 18. Early Christianity inherited it. Islam's zakat settles at 2.5% of savings, which sounds lower but is calculated on accumulated wealth rather than annual income and tends to land in a similar place for middle-income households.
Ten percent is not divinely efficient. It is, however, surprisingly sticky.
Peter Singer tried to revive the number secularly in 2009 with The Life You Can Save. A year later Toby Ord and Will MacAskill founded Giving What We Can, built around a Pledge: at least 10% of your income, to whichever charities you believe do the most good, for the rest of your working life.
The pledge has accumulated a specific, interesting data set. And the data shows 10% works, roughly, for people who aren't in financial distress.
The Schelling point
Ten percent is what economists call a Schelling point. A natural coordination value that people converge on even without explicit negotiation.
Try to design a pledge number from scratch. Five percent feels too low to be serious. Twenty-five percent is out of reach for most households with kids and housing costs. Ten is the number that sits right at the edge of uncomfortable but achievable, for most people in rich countries, most of the time.
As of late 2025, Giving What We Can reports more than 9,000 active pledgers collectively directing roughly $400M to high-impact charities since inception, with annual giving now above $50M per year. Pledge retention, per GWWC's own 2023 impact report, runs around 75% at five years out. That's high for a voluntary financial commitment.
The number works because it's a coordination device, not because it's optimal.
What the data actually says
Three findings worth sitting with.
Ten percent doesn't correlate with feeling poorer. Dunn, Aknin and Norton's 2008 Science paper, and the decade of follow-up work in the same vein, found that the hedonic impact of giving is roughly neutral-to-positive even at meaningful levels, controlling for income. People who give 10% of a middle-class income don't report materially lower life satisfaction than those who give nothing. Some studies suggest mild positive effects.
Most religious tithing data is consistent. Studies of Mormon tithing, Seventh-day Adventist giving, and devout Muslim zakat practice all show the same pattern. Long-term givers don't become poorer in any meaningful sense. They adjust spending patterns. Lifestyle creep slows. Housing and car decisions shift. The ceiling effect is real but starts much higher up the income distribution than people expect.
Sliding scales work better than flat percentages at the extremes. GWWC's own analysis led them to recommend a sliding pledge: Further Pledge from 1-10% for early-career or constrained pledgers, scaling up with income. Singer's original proposal in 2009 was explicitly progressive, ranging from 1% at the poverty line up to 33% at extreme wealth. The more rigorous the analysis gets, the more the flat 10% looks like a useful default rather than a universal law.
The practical bit
Three things to know if you're thinking about this.
First, it's pre-tax or post-tax, your choice. GWWC asks pre-tax for consistency but explicitly accepts post-tax if that's what you can commit to. The Pledge Form is designed to be honest, not extractive. Pledge what you can actually hold for a decade.
Second, where matters more than whether. A 5% pledge directed at GiveWell's top charities does roughly 100x the impact of a 10% pledge directed at the average charity, per GiveWell's cost-effectiveness estimates. The direction is the bigger decision than the percentage.
Third, it compounds weirdly. If you pledge 10% at 25, invest consistently, and give from the top of the income curve in your forties and fifties, the total given often exceeds 10% of lifetime earnings by a meaningful margin. Inverse-compounding, because you're spending less of your early income and letting your later income carry disproportionate weight.
The question underneath
The ten percent tithe is doing a specific thing. It's forcing a decision that most people never make.
Most households in rich countries give 2-3% of income to charity on average (Giving USA 2023 puts US household giving at roughly 2.1% of disposable income; the UK CAF UK Giving Report 2024 puts it around 1.3%). Those numbers have been flat or declining for twenty years.
Nothing about the data suggests 10% is the right number for everyone. But the act of picking a number, any number, and committing to it, changes giving from a reactive thing to a designed thing. That's probably where the actual leverage lives.
Sources used: Giving What We Can 2023 Impact Report, GiveWell cost-effectiveness analysis (2024), Dunn, Aknin & Norton, Science (2008), Singer, The Life You Can Save (2009, updated 2019), Giving USA Annual Report (2023), CAF UK Giving Report (2024). Full links in the planning doc.