As you might expect, that total number of dead people has grown a lot over time. The U.S. Census Bureau has collected several of the sources for historical world population rates. The estimates differ for two major reasons — the demographers don’t all agree about which date to take as the starting point for human life, and they also estimate population growth differently. Haub told me that he takes 50,000 B.C. as his starting point (based on research from the United Nations about when modern Homo sapiens may have first appeared) and assumes that population growth was pretty much constant until 1850 (wars and famine might make that assumption wrong, but who’s to really say given the absence of statistics offices in the Middle Ages?). Overall, then, he estimates that the human population grew from two people in 50,000 B.C. to 2.5 billion people in 1950.

As I said earlier (and as you probably guessed), most of those people who have been born are no longer with us. What’s really fascinating, though, is how the dead-to-living ratio is expected to change in the future. By 2050, the world’s population is expected to grow to 9.7 billion. Which means that in 35 years’ time, the living would make up 8.6 percent of those who have ever been born. And the dead would outnumber the living 11 to 1.

If you think those numbers are shaky (and you should, Shannah!), it gets shakier when it comes to more detailed demographics — you can forget about data on things like disability or migration. I tried to look at the basics: age, location and sex.