Think about the numbers

Colored numbers painted on the floor. Game for children.

This week, a little more of a thinking post. Ranty, a little, perhaps. Let me talk through some numbers I heard about today, and why they were true… but also completely false.

Lies, Damn Lies, and Statistics

I don’t know who the origin of that quote was. No doubt someone famous, if for no other reason than because they are now quoted regularly when talking about statistics.

Something I read today contained the following statement (paraphrased to protect the guilty):

This man has a failure rate of 60%, clearly showing that he was incompetent.

It went on to give the actual figures and details, and on approximately 300 goes at doing this thing, he had failed roughly 190 times. On the face of it, that sounds terrible, right? He failed to do something 60% of the time. More than half the time! I can’t tell you the actual details of this task, but the bald statement that he was incompetent, then backed up by the success figures given, has convinced you that the statement must be unequivocally true, right? The man is not just incompetent – you’re probably thinking he’s grossly incompetent. And it quotes the figures, so you know it’s true!

I don’t know the actual failure figures, but I do have some reasonable familiarity in this area. I strongly suspect the average failure rate for competent people doing this particular task is somewhere between 50% – 70%. That is, for people who know what they’re doing at this particular task, they will, on average, fail at it somewhere between 50% and 70% of the time. That is not just acceptable, it is inevitable because of how this system works. That puts the whole thing in a very different context, doesn’t it. Suddenly, a failure rate of 63% (approximately the actual percentage of his fails) is towards the top end of the range I have identified as normal. All of a sudden, he’s no longer “grossly incompetent”; he’s somewhere between “a little bit below average” and “above average”. The difference? Understanding what the numbers mean in their context, and not taking them blindly at face value.

Let me be clear – I do not think the author of that sentence deliberately set out to misrepresent the facts in this case. I do believe they had already formed an opinion, saw the failure numbers, and thought “Great, here’s something else I can pin on this person to prove my case!”, without actually thinking about the context in which those numbers occur.

Thirsty cows

My second example comes from something I heard on the radio this evening. The announcers were talking about vegetarianism, and one shared what it was that had convinced him that eating meat was bad for the planet. The issue of methane had already been discussed, and apparently Australian cows do not produce anywhere near the amount of methane as cows in the US do, because ours are mostly grass fed or grain fed – apparently cows in the US are usually more intensively grown, and are fed large amounts of corn and soy meal. While this produces meat that their market is used to, and allows high volume production, it isn’t what a cows digestive system is designed for. As a result, they produce large amounts of methane. I haven’t dug into this, but it sounds plausible. I can attest as a coeliac that eating stuff my body cannot process properly is prone to producing large amounts of methane! That wasn’t the bit that got my interest, however.

What as the thing that convinced this announcer that eating meat was bad for the planet (noting that methane was less of an issue in Australia)? The amount of water required. According to the figures he quoted, 500g of beef mince requires 1650 litres of water to produce. Not, despite my title for this section, because the cows drink that much. No, that is, apparently, the amount of water required to produce the pasture on which those cows are raised. Being good, environmentally conscious Australians, we are very aware of water shortages, and that sounds like a truly horrific amount of water to be used for just 500g of beef mince. However, the point of this blog isn’t to call bullshit on that number (although I am dubious about it).

Our water problem is a lack of water when we need it

The water problem in Australia does not come from redirecting rain to where the farmers need it. Despite what a small lunatic fringe no doubt believe, neither the Australian government nor any other body of people can control the weather and make it rain where they want it to. Our water problems come from the fact that this a dry continent with rainfall patterns not optimised for the growing of crops. And, to be fair, because we insist on growing crops not optimised for the climate in Australia. In order to ensure water is available when required for crop production and domestic use, it is necessary for us to harvest and store large quantities of water.

As noted above, in Australia most beef cattle are not force fed corn meal, and in fact, except in drought and (for some high-end products) the final finishing stages before butchering, they subsist pretty much entirely off paddock grown pasture. According to ABS, in 2014/15 about 10% of Australian meat products were fed on irrigated pasture (about 9.3% for beef, about 10% for other meats)1. So, regardless of the amount of water needed to grow food for the cows, in Australia it is not generally water being taken out of the natural system. In other words, it is not water otherwise available for irrigating crops or putting water into houses. It is water falling naturally where nature decreed.

Misleading use of numbers

The material this announcer has based his decision on is misleading (I cannot say “deceptive” because I have no evidence to indicate that the misleadingness was deliberate). By presenting the information in a particular way, it has invited you to draw a conclusion. While the numbers themselves may be true and correct, they have been presented in a way that draws you to a false conclusion. Reducing our beef consumption (or meat consumption generally) is not going to have any significant impact on water use and water shortage issues in Australia.

By way of contrast, 79.9% of vegetables grown for human consumption in Australia, 82.1% of fruits and nuts (excluding grapes), and 100% of rice, are grown with the benefit of irrigation. Don’t let that put you off being vegetarian, if that is your want – but please understand the realities of the numbers.

My message is…

So my message to you is this: When you see numbers used as a means to convince you of something, think about the numbers, and what they really mean. They may be completely true. They may even be backed up with evidence of how they were calculated. But despite all that, they may nevertheless be presented to you in a way that is completely misleading in the interpretation they are inviting you to draw. Think about the context in which those numbers are derived. Ask for (or research) more context. Make sure the numbers actually say what you are being invited to believe they say.


  1. ABS (2014). 4610.0.55.008 – Gross Value of Irrigated Agricultural Production, 2014-15.
    The figures quoted by the ABS in this report are in dollar values rather than gross tonnage, and I have been lazy and not attempted to dig up actual production amounts. I have, for the purposes of these calculations, made the assumption that product produced with and without irrigation sells for approximately the same value. Based on my Horticultural studies, I am confident that is a reasonable assumption.

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