LessWrong is currently reviewing the posts from 2018, and I'm trying to figure out how voting should happen. The new hotness that all your friends are talking about is quadratic voting, and after thinking about it for a few hours, it seems like a pretty good solution to me.

I'm writing this post primarily for people who know more about this stuff to show me where the plan will fail terribly for LW, to suggest UI improvements, or to suggest an alternative plan. If nothing serious is raised that changes my mind in the next 7 days, we'll build a straightforward UI and do it.

I've not read anything about it, so briefly, what is quadratic voting?

I'm just picking it up, so I'll write a short explanation it as I understand it, and will update this if it's confused/mistaken.

As I understand it, the key insight behind quadratic voting is that everyone can cast multiple votes, but that the marginal cost of votes is increasing, rather than staying constant.

With other voting mechanisms where cost stays constant, people are always incentivised to vote repeatedly for their favourite option. This is similar to how, under most scoring rules, people bet all their chips on the outcome they think is most likely, rather than spread their money directly proportional to their actual probability mass. You have to think carefully to design a proper scoring rule to incentivise users to write down their full epistemic state.

With quadratic voting, instead of spending all your votes on your favourite option, the more you spend on an option the more it costs to spend more on that option, and other options start looking more worthwhile. Your first vote costs 1, your second vote costs 2, your nth votes costs n. And you have a limited amount of cost you can pay, so you start having to make new comparisons about where the marginal cost should be spent.

Concretely, there are two things for a person voting in this system to keep a track of:

Votes is the total votes you make.
Cost is the total cost you pay for your votes

If you votes are

Post A: 5 votes
Post B: 8 votes
Post C: 1 vote

Then your numbers are:

Votes is 5 + 8 + 1 = 14
Cost is $(1 + 2 + 3 + 4 + 5) + (1 + 2 + 3 + 4 + 5 + 6 + 7 + 8) + (1) = 54$

This is a system that not only invites voters to give a rank ordering, but to give your price for marginal votes on different posts. This information makes it much more easy to combine everyone's...