The Parimutuel module implements a straightforward parimutuel market maker for categorical markets.
These are "losers pay winners" market makers: Any informant can bet any amount at any time. Their bet amount goes into the pot and they receive tokens which represent their share of the pot. After the market is resolved, the entire pot is distributed amongst those who wagered on the outcome that materialized, proportional to what their share of the pot is.
Selling shares is not allowed in parimutuel markets (this may be subject to change in the future). Parimutuel markets are only allowed to be used in conjunction with categorical markets; scalar markets are not allowed.
If there is no bet on the winning outcome, all bets are cancelled and informants can retrieve their funds from the pool, minus potential external fees paid to other parties.
- Collateral: The currency type that backs the outcomes in the pool. This is also called the base asset in other contexts.
- External fees: After taking swap fees, additional fees can be withdrawn from an informant's collateral. They might go to the chain's treasury or the market creator.
- Pot: The account that holds all the wagered funds.
- There's a hard requirement that the existential deposit of
Asset::ParimutuelSharesbe at least the existential deposit of the collateral used. This ensures that no whitelisting or other trickery is necessary to prevent the pot from getting dusted.