We start with world population data, spread it across countries and their time zones, work out the local hour for each of those groups, and apply typical sleep and wake probabilities for that hour. Awake plus asleep always adds up to the world population.
Nobody is counted, located or tracked individually. This is a model of humanity in aggregate — the last digits move because time moves, not because anyone was observed.
+Is this a real-time count of people?
No. It is a statistical estimate. There is no live census of who is awake anywhere in the world, so the number is modelled from population and local time.
+Are individual people being tracked?
No. No personal data is used or collected. The model only uses public, country-level population figures and time zones.
+Why does the number keep changing?
Because local time keeps changing. As dawn moves west across the planet, whole time zones shift from the sleeping side of the model to the waking side.