"There are approximately 7 billion people in the world. The average life expectancy is somewhere around 67.5 years. So in the next 67.5 years 7 billion people will die"
He's confusing average with actual.
Here's a simple example: imagine we have two people. 1 person who will die in 1 year, and 1 person who will die in 9. The average here is 5 years, and after 5 years only 1 person will be dead, not 2.
While It's not always true that selecting only individuals who have a value less than or equal to the average gets you half the population, this correct for normally distributed value when there are lots of samples, so the authors numbers are basically off by a factor of two.... which he almost notices here:
"So in the next 67.5 years 7 billion people will die. 67.5 years * 365 days is about 25,000 days. That’s about 280,000 deaths per day average. Right now that number is lower at about 155,000, but as the population ages that will catch up with us."
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