I will run an ultimatum game (1000 mana) among two randomly selected manifolders who participated in this market. 

Market resolves to Yes if the responder accepts the proposal.

Market resolves to No if the responder rejects the proposal.

One player, the proposer, is endowed with 1000mana. The proposer is tasked with splitting it with another player, the responder. Once the proposer communicates his decision, the responder may accept it or reject it. If the responder accepts, the money is split per the proposal; if the responder rejects, both players receive nothing.

More details about the ultimatum game on Wikipedia: 

https://en.wikipedia.org/wiki/Ultimatum_game

How the proposer and responder is selected:

At market closes, I will use #FairlyRandom to draw a random number to select the proposer, and ask the proposer to propose how to split the mana (in the comments section). Then I will randomly draw a responder, and ask the responder to decide whether to accept the proposal (in the comments section). *I will restrict the proposer and responder sample to those will less than 200 shares in the market, so that the ultimatum game incentives are not distorted by too much.  

If the randomly drawn proposer or responder did not make their choice in the comments section within 24 hours, I will randomly select another manifolder to replace them. 

The prize mana of the ultimatum game will be sent to the proposer and responder through manalink.