For reasons that I no longer remember I found myself looking at the murder rate page on Wikipedia. Looking at some of the patterns in a few of the safer countries I realized that I could estimate their populations based on their homicide rates.

Is that wrong?

Here’s a squished down copy of the bottom of that chart, showing homicides per 100,000 people per year. Can you see the patterns?

Monaco

There are only two numbers for Monaco – 0.00 and 3.1. It seems likely that this corresponds to years with no murders and years with one. Therefore that suggests that Monaco has a population of 100,000 / 3.1 = ~32,000

Iceland

Iceland’s numbers generally appear to be multiples of 0.34 to 0.35, with the recent numbers being 0.31. That suggests that the years with a murder rate of 0.31 and 0.35 represent one murder, o.65 represents two, 1.02 and 1.03 represent three, and so on. The declining rate for single-murder years suggests that the population has increased over the years, and is now about 100,000 / 0.31 = ~320,000

Bahrain

Bahrain’s numbers are a bit messier, especially the 0.94 in 2006. However the rest of them appear to be multiples of 0.11. That would give us a population of 100,000 / 0.11 = 910,000.

Morbidly conclusive

How’d we do? On the three countries with small enough populations and low enough murder rates to give us a plausible signal-to-noise ratio, two answers were quite good, and one was mediocre. I didn’t try any others.

Country Estimated population Actual Population Error Monaco 32,000 35,986 -11% Iceland 320,000 320,000 0% Bahrain 910,000 1,234,571 36%

The common divisor for Bahrain, given its population, ‘should’ have been about 0.081, rather than 0.11, but I can’t see that in the numbers. That could indicate dirty data, or a rapidly changing population.