A simplest form of the 80/20 rule says that 80% of results come from only 20% of efforts. For example, maybe the top two people on a team of 10 are responsible for 80% of the team’s output. Maybe the most popular 20% of items on the menu account for 80% of a restaurant’s sales. Maybe you read 10 books on a subject but most of what you learned comes from the best two (or the first two).
The exact numbers 80 and 20 are not special. For example, one study showed that 75% of Twitter traffic comes from the most active 5% of users. That’s still an example of the 80/20 rule. The point is that a small portion of inputs are responsible for a large portion of outputs.
One criticism of the 80/20 rule is that you can only know which 20% was most effective in hindsight. A salesman could call on 100 prospects in a week and only make sales to 20. At the end of the week he could ask “Why didn’t I just call on those 20?” Of course he had to call on all 100 before he could know who the 20 were going to be. Or maybe the best 20% of your stock portfolio accounted for 80% of your growth. Why didn’t you just invest in those stocks? If you could have predicted which ones they were going to be, you would have done just that.
It’s easy to be cynical about the 80/20 rule. There are too many hucksters selling books and consulting services that boil down to saying “concentrate on what’s most productive.” Thanks. Never would have thought of that. Let me write you a check.
At one extreme is the belief that everything is equally important, or at least equally likely to be important. At the other extreme is the belief that 80/20 principles are everywhere an that it is possible to predict the “20” part. Reality lies somewhere between these extremes, but I believe it is often closer to the latter than we think. In many circumstances, acting as if everything were equally important is either idiocy or sloth.
You can improve your chances of correctly guessing which activities are going to be most productive. Nobody is going to write a book that tells you how to do this in your particular circumstances. It takes experience and hard work. But you can get better at it over time.