One percentage point of annual wealth tax equals about a 20% tax on capital income if assets return 5% a year. That's the arithmetic Paul Graham set out in a May 2026 essay, dividing the wealth‑tax rate by the expected annual return on assets. The point is simple: a tax on stock and a tax on flow are only comparable once you pick a return assumption. For Australia the practical comparison must also fold in marginal brackets, the 2% Medicare levy and the 12% superannuation guarantee.

The read is straightforward. If you assume capital returns 5% annually, a 1% levy on wealth extracts the same cash each year as a 20% tax on that 5% income. Paul Graham set out the calculation in May 2026 to remind policymakers that a headline rate on stock and a headline rate on flow aren't directly comparable without an assumed return. The arithmetic forces the conversation away from labels and toward returns.

The arithmetic, step by step

The conversion rule is algebraically simple. Take the wealth-tax percentage and divide it by the expected annual rate of return on the assets being taxed. Using a 5% return, the factor is 1 divided by 0.05, which equals 20. That produces the headline equivalence: 1% wealth tax is about the same as a 20% tax on capital income.

Graham illustrates the mechanics with a $100 example. At a 5% return, $100 produces $5 of income in a year. A 20% tax on that $5 costs $1 in tax, leaving $4 of after-tax income and $104 in total. A 1% wealth tax on the $100 also costs $1 and leaves $104. The two regimes reduce after-tax accumulation by the same dollar amount when they share the same return assumption.

The assumed return drives the mapping. If the safe return falls to 4% the conversion factor becomes 1 divided by 0.04, or 25, so 1% wealth tax maps to a 25% income tax. Graham names 5% as his baseline and notes that lower long-run safe returns make a given wealth-tax rate equivalent to a higher income-tax rate. That historical sensitivity matters where safe returns have been low for extended periods.

What this means for Australian taxpayers

The simple arithmetic is necessary but not enough for policy. Who feels the pain depends on whether you compare marginal tax rates or effective tax takes, and on how the tax base is defined.

Mastheads

In Australia a straight conversion needs to sit alongside the practical tax settings people actually face.

Australian income-tax calculators for the 2025-26 year show marginal brackets of 0% on $0 to $18,200, 16% on $18,201 to $45,000, 30% on $45,001 to $135,000, 37% on $135,001 to $190,000, and 45% above $190,000. Add a 2% Medicare levy on top of those rates. Employer superannuation guarantee contributions are 12% of ordinary earnings and are paid on top of salary. Online Australian tax calculators and guides also point to PAYG withholding, HECS-HELP repayment thresholds and the superannuation guarantee as factors that shape take-home pay.

Those operational frictions mean a headline equivalence such as 1% wealth tax to 20% income tax doesn't automatically translate into identical distributional outcomes. Tax advisers and taxpayers who care about cashflow and withholding will emphasise timing, realisation of gains and how capital income is assessed. Australia treats net capital gains as assessable income in the year they're realised, and for assets held longer than 12 months individuals normally receive a 50% discount on the capital gain before inclusion. That interaction changes the effective tax on realised capital gains compared with a standing wealth levy.

Concrete examples make the point. A worked example in the brief shows that someone on $85,000 of taxable income ends up with an effective tax rate near 21.2% once offsets and the Medicare levy are included, even though part of their income sits in the 30% marginal bracket. That effective rate sits close to the Graham conversion for a 1% wealth tax at 5% returns, but the groups exposed are different: the $85,000 earner is paid in wages, while the owner with $100 of capital earning 5% is exposed to taxation on capital stock or capital flow.

Policy choice is therefore about incidence and administration as much as arithmetic. A wealth tax targets accumulated stock and most directly affects owners of financial and real capital, retirees living off returns and high net worth households.

An income tax targets flows and often lands on wage earners via PAYG withholding. The conversion anchors the scale of those choices, but it doesn't resolve behavioural responses, asset valuation issues or collection costs that matter in practice.

I'd argue the practical takeaway is this: if politicians propose a wealth levy, ask what return assumption underpins their equivalence claim. The assumed rate will determine the income-tax analogue and therefore the political story the measure tells about fairness and burden sharing.

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If politicians pitch a wealth levy, scrutinise the return assumption and compare it to Australia’s Stage 3 brackets. The 2025-26 calculators already fold in the 2% Medicare levy, HECS repayment thresholds and the 12% superannuation guarantee when estimating net take‑home pay.

This article was created with AI assistance.