What is quadratic voting, and could it fix one person, one vote?

The problem it tries to solve

A yes/no ballot counts how many people prefer each side. It can't count how much they care. If 51 people mildly prefer A and 49 people would be badly hurt by it, A wins 51 to 49. Preferential voting, which Australians use, ranks the options, but a ranking still doesn't say whether your first choice matters to you a little or enormously.

Economists have known since Kenneth Arrow's work in 1951 that any system built only on rankings runs into hard limits. Quadratic voting steps outside rankings: it asks for strength of feeling as well.

How it works

Everyone gets the same number of voice credits, say 100, to spend across a slate of questions. Casting votes on one question costs the square of the number of votes:

Votes on one question	Credits it costs	Cost of that last vote
1	1	1
2	4	3
3	9	5
5	25	9
10	100	19

So you can spread 100 credits as one vote on each of 100 questions, or put all 100 into ten votes on the one question that matters most to you. You can vote for or against.

Back to the 51 and the 49. If each of the 51 spends one credit, A gets 51 votes. If each of the 49 spends 25 credits on five votes, B gets 245. The group that cares more wins, and pays for it with influence it can no longer use elsewhere.

Why the square

With a square cost, each extra vote costs a little more than the one before. Economists Steven Lalley and Glen Weyl showed that in large groups this pricing leads people to buy votes in proportion to how much the outcome matters to them, which is what a fair total of everyone's interests needs (Lalley & Weyl, 2018). A flat price lets anyone who cares at all pour everything into one issue. A steeper price muffles strong feeling.

The idea's first version, from Eric Posner and Glen Weyl, had people buy votes with money (Posner & Weyl, 2015). Most trials since use an equal budget of credits instead, so wealth buys nothing.

Where it has been tried

Where	What happened
Colorado House Democrats, 2019	Each member got 100 tokens to set priorities among 107 possible bills. The Equal Pay for Equal Work Act came out on top.
Colorado courts, 2024	A Denver judge ruled the caucus's anonymous quadratic ballot on spending priorities broke the state's open meetings law. The method could stay; the votes had to be public.
Taiwan Presidential Hackathon, 2019	Quadratic voting, with a budget of 99 points, helped pick the winning projects.
Surveys	A 2017 study found quadratic-voting surveys picked out people's strongest views more clearly than ordinary agree/disagree scales (Quarfoot et al., 2017).
Grant funding	A cousin, quadratic funding, matches donations so that many small donors count for more than one large one (Buterin et al., 2019). Gitcoin reports distributing over US$60 million this way to more than 3,700 projects.

What can go wrong

Fake identities

The square cost only works if each person has one budget. Ten fake accounts with 10 credits each buy far more votes than one real account with 100. Any public use needs strong proof that each voter is one real person, and that proof sits uneasily with privacy.

Teaming up

Ten people casting one vote each spend 10 credits. One person casting ten votes spends 100. Groups who coordinate get more for their credits. Weyl argues that in an electorate of a million, collusion would need thousands of people to matter, and that laws against it would help (Weyl, 2017). How well that holds in practice is untested.

Secrecy versus accountability

Colorado shows the tension. Citizens need a secret ballot. Politicians' votes need to be public. A quadratic system must be built for the right one.

Harder to explain

People must understand the price rule to trust the result. Trials so far used small, motivated groups. Nobody yet knows how a whole electorate would take to it.

Who writes the questions

You can only spread credits over the questions on the list. Whoever sets the list shapes the outcome.

Where it fits

Quadratic voting suits a slate of many choices: a council budget, a list of projects, a survey of priorities. It adds little to a single yes/no question, because with one question everyone just spends everything on it. It doesn't replace elections. It could sit beside them, in places like participatory budgeting, where people already pick among many options.

Try it

Take ten things your local council could fund. Give yourself 100 credits and price votes as squares. See where your credits go, then compare that with a single tick for your favourite. The gap between the two is what quadratic voting tries to capture.