This market will resolve YES if and when each of the following three world population counters displays a number greater than 8.4 billion: Worldometer; Population.io; The world counts.

The resolution date for this market will shift based on market odds. It will move closer as the odds increase, and further into the future as the odds decrease. This will allow for an assessment of when the resolution event will occur. Initially, with 50% odds, the resolution date is set 50 years in the future. If the odds rise to 75%, the resolution date changes to 25 years in the future. At 80%, it changes to 10 years; at 90%, to 5 years; at 95%, to 1 year; at 96%, to 3 months; at 97%, to 1 month; at 98%, to 1 week and at 99% to 1 day in the future. I have a predefined list of resolution dates for each value between 1% and 99% odds and will adjust the resolution after each trade that changes the odds by at least 1%. 

The market will never resolve to NO, since there can be no proof that the world population will never reach 8.4 billion.