I didn't downvote it, but: While total ignorance of statistics might lead you to expect suicide rates to be wildly unpredictable, and knowing a bit of statisti

I didn't downvote it, but: While total ignorance of statistics might lead you to expect suicide rates to be wildly unpredictable, and knowing a bit of statistics might make it obvious that they shouldn't be, knowing more statistics should make it not-obvious again. So, from a position of total ignorance you might say: suicide rates are the result of lots of individual freely made decisions, and should therefore be completely unpredictable. Then if you know a bit of statistics you might say: no, the population's suicide rate is the average of the individuals' suicide rates, and averaging things reduces their variance so we should expect it to be quite predictable. But if you know a little more statistics, a few other things will occur to you. The first is a red herring: averaging things only reduces their variance when the variance is finite. Standard counterexample: mount a gun or laser or something on a swivel mount with a 180-degree range near an infinitely long wall. Point it at a random angle and see where it hits the wall. This gives you a position with the so-called Cauchy distribution, and the average of a million of these has the exact same distribution as a single one. (That doesn't mean you can't extract information from having lots of samples; e.g., the median is nice and informative. It just means that taking means isn't the way to do it.) Why is that a red herring? Because an individual's suicide-or-not during a given year can only take the values 0 and 1, and therefore its variance can't be larger than 1/4 (and in particular can't be infinite). So averaging together lots of these should give you something well-behaved, right? Not so fast. Those individual suicide-or-not random variables may be correlated (e.g., when Goethe published his gloomy book "The sorrows of young Werther", whose protagonist -- SPOILER WARNING -- kills himself at the end, a wave of copycat suicides swept across Europe). And they may depend on something that varies with time (the same example will do nicely, but you might also consider economic conditions, weather, polluted water supplies, etc.), and there's no reason why that something (or those somethings) shouldn't swing around wildly. So no, it isn't altogether obvious to anyone who knows some statistics. It shouldn't be a big surprise if in fact suicide rates are pretty well behaved, but I think if you think it's obvious then you're not thinking hard enough.