Slippery Numbers


You know numbers, at least so-called rational numbers, seem like pretty simple things. After all, three beers is three beers and it seems to be a fairly simple concept to grasp. And yet time and time again I write about these ideas precisely because very smart people get all mixed up and confused when it comes to these little bastards that we call “numbers” and use as a form of first order semiotics.

UPDATE: Okay the original tweet from this guy has been deleted but what it said was “If the life expectancy of someone in Romania is 69 and the retirement age is 65 then you work all your life for a pension for just 4 years” or something to that effect.

I’m not really picking on this guy except that he runs his own business school here in Romania and he really should know better. But lots and lots of other smart people get tripped up on these kinds of things all the time.

On the face of it, what he said seems correct. If you retire at age 65 and are only expected to live until age 69 then you only get to enjoy your retirement for four years. So what’s wrong here?

What’s wrong is that the number 69 means the projected life expectancy at birth. A baby born today is expected (statistically speaking) to live until 69 years old. But some people will die in infancy or childhood or as young adults. The fact is that the longer you live, the better your chances are of continuing to live. The real question that he should be asking is “what is the life expectancy of a 65 year old person?” And while I don’t have any actuarial tables for Romania here in front of me, I’d guess that if you’ve survived until age 65 you probably have another twenty years ahead of you before you die.

If I make this kind of mistake in a blog post and nobody gives a crap what I say, then it’s fine. But when you start being in positions of authority and responsibility, like running a business school, then that’s where you run into trouble. And when it gets to the “lofty heights” of international finance, massive billion euro loans from the IMF and other such subjects, why then you’re walking a very fine tightrope indeed.

I mean I’ve already talked about Ion Stan who stated openly that he thought Romania’s GDP was off by a staggering 20%. That was fine fodder for the news channels when he was a no-account member of the minority party but now Victor “Skeletor” Ponta is likely to be the next Prime Minister and Mr. Rus is going to be a member of the ruling coalition (they’re both in the same party). What then? What happens when people in power start casting doubts and aspersions (or incorrect logical conclusions) concerning numbers? I shudder to think.

Want to test your own abilities? Here’s a fun classic with a Romanian twist:

If 3 men can eat 3 mici in 3 days, how many mici can 6 men eat in 6 days?

Take your time and then when you’re ready use your mouse to highlight the answer below:

If 3 men can eat 3 mici in 3 days, then 6 men can eat 6 mici in 3 days. So in 6 days, the 6 men will be able to eat twice as many mici as 6, which is 12.

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