The idea that relatively few factors are the cause of the majority of cases. This is often referred to as the 80-20 rule: 80% of the problems are created by 20% of the causes.

An example: 80% of the machine breakdowns is caused by 20% of the machinery. There is not a one-to-one connection between machine and breakdown so solving the problem is a less overwhelming task. Once one has identified the problem machines, they can focus on those instead of fixing each and every one.

A different spin: 80% of the purchases are made by 20% of shoppers. Once a firm has identified those shoppers, they can start treating them specially and offering special promotions. Ever had one of those buy 9 coffees get the 10th free cards? That is the Pareto concept applied.

Pareto on E2?: 80% of nodes are created by 20% of noders. The rest of us just can't get past novice - argh!

NB: Pareto analysis is named after 19th century Italian economist Vilfredo Pareto.

There is that rule. I don't remember where I heard it, neither do I know who first thought of it, but it basically states that

FIRST 20% OF WORK IS DONE IN FIRST 80% OF TIME GIVEN,
AND LAST 80% OF WORK IS DONE LAST 20% OF TIME.

I recall that when it was mentioned it was applied to programming, but it generally applies to everything (no, other everything).

Also the main trick of this rule is it's Recursiveness.

It can be applied again to the 20% of time and 80% of work we have left. And to new values we get.

Eventually, if you plot a graph of work left to time left till the deadline, you will get a hyperbola
(with time aproaching 0, relative work aproachesINFINITY)

grr, ok I will post it here, but only to make antonz Sit the fuck down, and Shut the fuck up!
This rule applies only to personal projects, stuff that you write on your own! For team projercts, this rule is inversed!
Vilfredo Pareto was a 19th century statistician, economist, and sociologist. He is most famous for his discovery that holds true in all cultures (agrarian, technological, foraging, etc.) that the distribution of wealth remains at 80-20. Better said that 80% of the wealth in a society is owned by 20% of the people. This is what as known as Pareto’s Law, and commonly thought of as the “law of the trivial many and important few.” This law however doesn’t stop with the distribution of wealth it can be seen over and over. We are all familiar with the phenomenon in group projects. 20% of the people end up doing 80% of the work. It is also used in stock analysis, engineering, and consumer spending to name a few.

The actual equation is this:

Let N= the number of employed who have incomes greater than x
A & m are constants

Log N = log A + m log x
This is also a general rule of business.

Consider IBM-
80% of their profit comes from only 20% of their customers(the larger customers)
20% of their profit comes from the other 80% of their customers (the smaller ones)

Consider E2-
20% of the writeups have garnered about 80% of the total votes that have been used while
80% of the writeups have fewer votes (either way) and only have 20% of the total votes used

This rule can apply to many other statistical aspects where there is a human interest or business factor that directly influences two quantities such as those shown above. It is only a generalization to remind people where their priorities (are|should be).

This comes in two forms: one where you are free to reorder the owning set, and one where you are not.

If you are free to reorder the owning set, for any distribution of the commodity, you can find some fraction n for which the top n of the set has 1-n of the commodity. If every individual has the same amount, then n and n-1 are both 50%. The extremity of n can be used as a measure of the imbalance of the distribution. Note that in this version, n can always be chosen not to exceed 50% since if 60% of the people have 40% of the money that implies that the other 40% have 60% of the money...

The case where you are not free to reorder the owning set essentially describes the behavior of any nondecreasing function f such that f(0) = 0, f(1) = 1, and f(x)<1 for all x on the region (0,1). These functions can describe the amount of partial progress in a process that takes finite time. Look how much of the end goal you have accomplished after doing a fraction n of the work required to achieve that goal.

If filing your nails to perfection takes 1 minute each, how close to perfection do you get if you file each for 10 seconds? If building a hut takes a week, how much shelter do you get out of the first day's work?

So long as your progress is always positive, there will only be one point for which f(n) = 1-n, so you can construct a n/1-n rule from it. If the greater part of the benefit is upfront, then n will be low and 1-n high (probably the case with the nails, as you will have smoothed them out); if the greater part of the benefit comes only after most of the work, you can get n high and 1-n low (probably the case with the hut - a framework won't be all that useful for sleeping under).

In both cases, n cannot be 0 or 1. In the first case, that would imply that a) everyone has nothing, and b) no one (0% of the population) has everything (100% of the commodity), which is an unfortunate situation.
In the second case, n = 0 would imply that you don't need to do anything to achieve everything, and n = 1 would imply that even if you do everything you don't get anything done.

The common 20%-80% form is simply a common degree of imbalance.

I find it amusing that we have 2 "--mancer" at this node... death and dreams...

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