Conversation so far:
when will the world population hit 8 billion
According to current projections, the global population will reach eight billion by 2024.
which continent makes up the highest proportion of the world population
Asia is the most populous continent, with its 4.54 billion inhabitants accounting for 60% of the world population.
which country in asia has the highest population
China is the country with the highest population in Asia.
what is the largest ethnic group in asia
The Han Chinese are the world's largest single ethnic group, constituting over 19% of the global population in 2011.

Question: what is the most-spoken first language
Self-contained rewrite: what is the most-spoken first language in the world