I didn&#x27;t downvote it, but:<p>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&#x27;t be, knowing <i>more</i> statistics should make it not-obvious again.<p>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.<p>Then if you know a bit of statistics you might say: no, the population&#x27;s suicide rate is the average of the individuals&#x27; suicide rates, and averaging things reduces their variance so we should expect it to be quite predictable.<p>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 <i>the exact same distribution</i> as a single one. (That doesn&#x27;t mean you can&#x27;t extract information from having lots of samples; e.g., the <i>median</i> is nice and informative. It just means that taking means isn&#x27;t the way to do it.)<p>Why is that a red herring? Because an individual&#x27;s suicide-or-not during a given year can only take the values 0 and 1, and therefore its variance can&#x27;t be larger than 1&#x2F;4 (and in particular can&#x27;t be infinite). So averaging together lots of these should give you something well-behaved, right?<p>Not so fast. Those individual suicide-or-not random variables may be <i>correlated</i> (e.g., when Goethe published his gloomy book &quot;The sorrows of young Werther&quot;, whose protagonist -- SPOILER WARNING -- kills himself at the end, a wave of copycat suicides swept across Europe). And they may depend on something that <i>varies with time</i> (the same example will do nicely, but you might also consider economic conditions, weather, polluted water supplies, etc.), and there&#x27;s no reason why that something (or those somethings) shouldn&#x27;t swing around wildly.<p>So no, it isn&#x27;t altogether obvious to anyone who knows some statistics. It shouldn&#x27;t be a <i>big surprise</i> if in fact suicide rates are pretty well behaved, but I think if you think it&#x27;s <i>obvious</i> then you&#x27;re not thinking hard enough.