Here’s what happens when you don’t have a good intuition for numbers, or Number Gut:
For example, there was news story published back in the late 80s that reported that the state of New Jersey produced 50 billion used tires every year which caused a huge environmental problem. The story got widely disseminated before somebody pointed out that since New Jersey had a population on only around 8 million, 50 billion tires a year came out to 6,250 tires per capita per year. The story got play because the editors had no intuitive feel for the significance of 4 orders of magnitude difference between the size of the population and the tire consumption.
A more recent (and even more political) example, the Lancet Iraqi Mortality Survey (LIMS):
A lot of people who would know better in another context seem perfectly willing to swallow the estimate of 300,000+ dead that LIMS reports with the Falluja cluster included. Examined in detail, LIMS reports that of those 300,000, roughly 250,000 died from violence, and of those something like 220,000 died from Coalition airstrikes. The LIMS authors even suggest [p6 pg7] that this is likely an underestimate.Anyone with a good number gut for such phenomenon would immediately recognize such numbers as implausible.
Why couldn’t 250,000 be dead from violence? Well, the first clue is that the total population of Iraq is around 25 million, so 250,000 dead represents 1% of the entire population. That means if LIMS is accurate then 1 in every 100 Iraqis were killed in the war up to Sept 2004. So what? After all, it’s a war and lots of people die in wars right? Well, not as many as most people think.
For example, during WWII the Japanese mainland suffered the most extensive aerial bombardment in history. Every major urban area save one (Kyoto) was burned to the ground. On march 10th, 1945 the great Tokyo fire raid burned down a third of the city and killed 100,000 people. Two major cities were nuked. Japan at the time had a population of 78 million, so 1% of the population would have been around 780,000. Now, what is your guess as to the number of Japanese killed on the Japanese mainland?
Did you guess around 500,000? Under 1%? Well, that is in fact the number (note: that’s only dead, not dead-and-wounded).