75% of the earth’s population, an estimated 4 billion people, who have no address for mailing purposes. – WTF Fun Facts
Source: https://qz.com/705273/mongolia-is-changing-all-its-addresses-to-three-word-phrases/
WTF Fun Fact – Missing Mailing Address

But these are microwaves, aren’t they ?
The world population in 2016 (when the source article was written) was ~7.5 billion. 75% of 7.5 billion is 5.625 billion, not 4 billion.
The math doesn’t fit.
I believe the number’s close to 6 billion since there’s 7.8 billion people on the planet.