80-20, 90-10, Pareto, tall bar, long tail what is all that? Does it always work?

Supposedly it is a magic recipe that shows how to get a lot of benefits from little work. Everyone says it, but in your experience does it work? Let’s have a look, focusing on the main items (and ignoring pedantic details.)

Imagine you are at the beach with your children. Watch them as they collect ten pebbles, put them on the table and make all sorts of patterns with them. At one point they put eight of the pebbles in one line, and two on the other. That’s 80% in one line and 20% in the other. Is that the famous 80-20? If they move one pebble from the shorter line to the longer one, giving nine and one, is that 90-10? Well, it is *a* 90-10, but it is not *the* 90-10. If I do 10% of the work (move one pebble), I get 10% of the result — the pebble is in the other line, I don’t see what’s the supposed big benefit here — the result is in direct proportion to the effort; in other words, in this situation, 90% of the benefit requires 90% of the work not 10%.

A lot of our daily experience is like that. When I go to the strawberry pick-your-own, what I have to pay the farmer, her benefit, is in direct proportion to the weight of the berries. At the cinema, the take is in proportion to the size of the audience. It could have been in proportion to the number of minutes, like it is for long distance phone call, but they don’t do it that way… Hey, wait a second… so there is a choice in what is counted as effort.

If I have one hundred issues in my bugs backlog, and I fix ten of them, I’ve obtained 10% of the way to eliminating my backlog. Or if I have one hundred customers to contact, and I have contacted ten of them. I’m 10% done… So the benefit is proportional to the effort. Really? Which benefit are we talking about? Sure, if the benefit is getting tick marks next to all to-do items, that is correct. If the benefit is the percentage of the work to be done, considering each item might take differing amounts of work or time, then, on average I’ll be around 10% done. But what if the benefit has to do with the value gained when looked at from a different point of view? What if the 10% of customers I contact are the only ones that will buy that week? Or the 10% of the bugs I fix are the only ones that customers hit? That 10% of the effort yields 100% of the benefits in those specific cases. Or I could be unlucky, and the 10% of the effort just happens to be put on those items that will give 0% of the benefit.

One lesson here is that there is a caveat with 90-10, or 80-20. Those formulations happen to add up to 100, so it is very natural to want to add them up, but they do represent different things. Remember, usually when we say 90-10, we mean that 90% *of the benefit* is obtained with 10% *of the effort* The first number has to do with the benefit and the second has to do with the effort. In 90-10 and in 80-20, the numbers happen to add to 100. I think this is intended to make it memorable, but I just find it misleading.The reality is that you are adding different thing — it could be 0-10 or 100-10 or anything between. There could be no connection between them, or a proportional connection, or an outsized connection. It depends entirely on what is meant by benefit, and what is meant by effort.

Incidentally, in the story with the children, what if the pebbles are of all different sizes, one of them much bigger than the others, and that the smallest is actually a diamond… makes you think about value vs effort, doesn’t it? And from whose point of view, yours or the children’s?

The key observation is to look at benefit vs effort, and see if one can take advantage of those «leverage» situations where the percent of benefit is much greater than the percent of effort.