The Pareto Principle: 80/20 rule.

The Pareto Principle was discovered when Vilfredo Pareto observed that 80% of the land in Italy was owned by just 20% of the population. Since then, many other people in different disciplines have observed similar 80/20 distributions.

In programming this often means that the last 20% of a development project can require 80% of the cost. Knowing this, it would make sense to concentrate on producing a 80% solution; this would happen if you use the "worse is better" philosophy.

It seems that the same principle can also apply to car repair. My car had been sluggish and inefficient recently, so I went to the garage today. The mechanic examined the engine and determined that the problem was a build-up of carbon on the valves that stopped them closing correctly. He told me that the correct way to fix this problem was to remove all the valves and clean them by hand: this would cost at least �200. He didn’t do that. Instead he sprayed decarboniser into the pipes and recommended that I buy a fuel additive. The total cost of this option turns out to be about 20% of the correct solution.