Hard Tweets Explained: Barrels of Babies

This tweet isn’t really all that hard, but I thought it would be fun to document how I arrived at my number. I actually tweeted a different conclusion in an earlier tweet, but in writing this story, I noticed an oversight. So here we are.

In case you aren’t aware, a “barrel” is a precise unit of volume measurement. When they talk about Venezuela producing 2.5 million barrels of oil a day, that’s about how much oil there is, not literally how many barrels they use, because I don’t think anybody puts oil in barrels any more.

A “barrel” is 119.2 liters.

I cannot fathom what made me curious about how many barrels of babies are produced each year. Clearly I need to adjust my medication. But to figure this out, we need to know how many babies are produced.

Surprisingly, google was pretty lame at answering that for me. However, I eventually stumbled upon the CIA web site (yes, that CIA) which revealed a birth rate of 18.9 births per 1000 population, and a world population of 7,095,217,980. So 18.9 times 7,095,217 = 134 million babies.

Next, we need to know how much volume a baby takes up, in liters. It turns out nobody has done an Archimedes-style experiment of putting a baby under water and seeing how much the water rises. Slackers.

Archimedes as a child

So I need to estimate. Using the Nirvana album cover as inspiration, I’m going to guess that babies have a similar density to water. So if I find out how much the average baby weighs, I can guess how much volume it takes up by guessing it takes the same amount as that weight of water. Google is helpful here: it offers that the average birthweight worldwide is 3.4 kg (7.5 lbs). A fun fact about the metric system is that 3.4 kg of water consumes 3.4 liters. So we are going to guess that each baby takes up 3.4 liters of volume.

So our 134 million babies take up 455.6 million liters. Divide that by 119.2 and we have 3.8 million barrels.

Homework: Borrow a 7.5 lb baby and do the Achimedes experiment to find out if my estimate is correct.