Freakonomics reports:
A reader in Norway named Christian Sørensen examined the height statistics for all players in the 2010 World Cup and found an interesting anomaly: there seemed to be unnaturally few players listed at 169, 179, and 189 centimeters and an apparent surplus of players who were 170, 180, and 190 centimeters tall (roughly 5-foot-7 inches, 5-foot-11 inches, and 6-foot-3 inches, respectively). Here’s the data:
It’s not costless to communicate numbers. When we compare “eighty” (6 characters) vs “seventy-nine” (12 characters) – how much information are we gaining by twice the number of characters? Do people really care about height at +-0.5 cm or is +-1 cm enough?
It’s harder to communicate odd numbers (“three” vs four or two, “seven” vs “six” or “eight”, “nine” vs “ten”) than even ones. As language tends to follow our behaviors, people have been doing it for a long time. We remember the shorter description of a quantity.
This is my theory why we end up with more rounded numbers. This is also partially why Benford’s law holds: we change the scales and measurement units as to enable us to store the numbers in our minds more economically. Compare “ninety-nine” (11 characters) with “hundred” (7c), or “nine hundred ninety-nine” (24) with “thousand” (8c).
For our advanced readers, let me give you another example. Let’s say I estimate something to be 100. The fact that I said 100 implies that there is a certain amount of uncertainty in my estimate. I could have written it as 1e2, implying that the real quantity is somewhere between 50 and 150. If I said 102, I’d be implying that the real quantity is between 101 and 103. If I said 103, I’d be implying that the real quantity is between 102.5 and 103.5. If I said 50, the real quantity is probably between 40 and 60.
This way, by rounding up, I have been both economical in my expression but also been able to honestly communicate my standard error.
Eventually, increased accuracy is not always worth the increased cost of communication and memorization.
So, do you still think World Cup players are being self-aggrandizing, or are they perhaps just economical or even conscious of standard errors?
[D+1: Hal Varian points to number clustering in asset markets. Also thanks to Janne helped improve the above presentation.]