If you buy stock in an idea, you’re basically saying two things:

1. you think the idea is valid, and

2. you expect other people to see its value in the future.

If the idea goes up in value, you earn money. If it drops, you lose money. That simple.

There are several ways a system like this could work:

1. Buy at the “agreement price”

One option is to set the price of an idea at the percentage of people who agree with it, plus a small service fee—say three cents per transaction.
This keeps the system stable. If more people cash out than pay in, the market goes broke, so the service charge creates a cushion that keeps everything running.

2. Rate ideas more deeply than “agree/disagree”

Another approach is to score each idea on several qualities—how clear it is, how logical it is, how practical it seems, how fair it is, how peace-promoting it might be, and so on. Each quality could be rated from 1 to 10.

People could also submit reasons to defend their ratings. Others could vote on those reasons, pushing the strongest ones to the top of the “pro” and “con” lists. In this system, the “value” of an idea isn’t just popularity—it’s how strong and well-supported the arguments are.

3. A free-market system

In a looser system, people could buy and sell idea stock at whatever price others are willing to pay. The challenge is supply and demand: on a site full of thousands of ideas, why would any one idea be worth more than another?

One solution is to limit the market to the top 100 ideas. You could also set a time window—like a six-month buying period—so people focus their attention and the market stays active.