Sleeping population simulation
What fraction of the world is asleep right now?
Inspired by a tweet asking, “Is there a time when nearly all of humanity is asleep at the same moment?”, I simulated global sleeping population rates across different hours using open demographic datasets.
Methodology & Assumptions
I used the Gridded Population of the World (GPWv4) dataset provided by NASA / Columbia University's Socioeconomic Data and Applications Center (SEDAC).
- Population Aggregation by Longitude: Approximated local time zones using degrees of longitude, aggregating global population density across each longitudinal slice.
- Sleep Window Assumption: Simply assumed that people sleep for 8 hours between 10:00 PM and 6:00 AM local time.
At 7:00 AM JST, Roughly 74% of the World Is Asleep
Because Earth's landmass and population are heavily skewed toward the Eastern Hemisphere (where over 80% of humanity resides), the calculations revealed an extraordinarily pronounced wave.
- Peak (07:00 JST): When it is late night in Europe, the small hours in India, and early morning in China, approximately 74% of the global population is asleep simultaneously.
- Trough (22:00 JST): Conversely, during evening hours across Asia, only about 3% of the world is sleeping. Maybe that's a good time to announce products.
While a single moment where all of humanity sleeps at once does not exist, this visualization captures the dynamic, planetary-scale wave of sleep driven by the uneven distribution of human population.