One of the biggest assumptions our society is founded in is that humans have, more or less, direct control over their actions. But science has in recent decades been winnowing the potential mechanisms for this to operate, suggesting more and more that humans are fleshy algorithms who respond to stimuli in complex and interesting but ultimately automatic ways.

Market runs for a long time because it seems like this might not be resolved for a good long while. I expect this market to extend if resolution is not clear at the end date.

Resolution criteria for this is obviously hard as it's going to depend on as-yet unknown evidence, so I'm going to float a few suggested resolution criteria and open the floor to more suggestions.

Resolves NO if an AI is able to reliably predict human responses to stimuli 99.9% of the time ten or more minutes into the future in a variety of situations.

Resolves YES if a mechanism explaining free will is found within human biology that defies prediction through biological process.

Resolves as per unanimous agreement of a council of interdisciplinary scientists (e.g. physicists + neurobiologists + philosophers) of international repute.

Disclaimer: whether or not free will is real (and even a 0.01% chance of YES means you should not assume NO given the impact either way), feeling like you have free agency is important for your mental well-being. If you feel you have no free will then I'd recommend seeking help from friends or therapists. Also, this market favouring NO does not absolve you of responsibility or the consequences of your actions, you are not merely a ball on the pinball table of an uncaring, pinball-playing good and someone somewhere will care if you think that you are.