Which year will the population of humans on January 1st be less than the population of humans on January 1st the year prior for the first time in recorded history?
This includes all humans not on Earth as well. This question doesn't ask when population will peak; human population may well continue to increase the following year. Assuming it is still active, https://www.worldometers.info/world-population/world-population-by-year/ will be used as the reference.
Population models from the United Nations predict that this may happen within the next hundred years. https://en.wikipedia.org/wiki/File:World_Population_Prospects.svg Although, a number of reasonable possibilities may break these models. An existential risk materializing could make this sooner than expected. All the while, faster than expected economic growth and decreasing cost of living, the colonization of space, or even a cultural or technological change in how humans reproduce may mean a never decreasing population.
