People often complain that some large/long-term markets are dominated by whales, who can outspend everyone else. In particular, some users are willing to spend much more on long-term markets than other users and so have an outsized influence on Manifold's long-term forecasts. I think one way to address this would be to see what difference it would make if some markets had a spending cap.

This could be an option when creating a market to click a box that prevents anyone trading in the market from spending more than 100 mana, or perhaps instead prevents them from holding more than some number of shares. 

The idea is that this might let you get something in-between a normal market and a poll, where average opinion would be weighted a bit more than track record and where interest rates wouldn't be as much of a concern because it's only a trivial amount of mana for everyone involved.

It could also mitigate newstrading, as the first person to see breaking news that resolves a market could not claim of the excess liquidity.

I think it would really be worth trying at least as a trial run, and comparing the accuracy of these capped markets to uncapped markets. This resolves yes even if this is just tested out, but not adopted permanently. 