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# Applying the Pareto Principle (80-20 Rule) to Baseball

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I was checking out Freakonomics blog and came across this questions answered section.  In it, David Berri and Martin Schmidt answered questions on their newest book, "Stumbling on Wins."  They mention that stars are really important for teams to wins and state that:

About 80% of wins appear to be produced by 20% of the players.

The theory behind this statement is the Pareto Principle or 80-20 rule. It states that 20% percent of a population does 80% of the work. The principle was developed by Vilfredo Pareto, who noticed that 20% of his pea pods produced 80% of his peas. He moved on to show that 20% of the world's population control 80% of the wealth. The principle has been used in software design, customer service, health care and criminal behavior.

I decided to look to see if this was true with major league baseball players. I took all players in 2009 and looked to see how much WAR (Rally's WAR database) was created in the top 20% of the players and the amount in bottom 80%. I put all players together and did not group depending on amount of time or negative WAR.

A total of 1263 players were divided up. The top 20% of all players generated 945 WAR while the bottom 80% generate -89 WAR. This works out to the top 20% of all baseball players generating 110% of the results. The numbers here aren't ideal so I adjusted the percentages to look at 15% and 10% of all players. Here is a chart of the results:

 % of Players % of WAR 20.0% 110.4% 15.0% 85.3% 10.0% 78.3%

So 15% of the all the players last year produced 85% of the total wins with the other 85% of the players creating 15% of the wins. The Pareto Principle holds up pretty soundly when it is applied to baseball last year.

Baseball's model fits closely into the model of a store. The store will get most of its profits from a small sample of people. These are the regulars that come in everyday and make their large purchases at the store. Most of the other people will come in for just few items once in a while.  Also there will be a set of people that end up costing the store money through lost productivity or theft.

Like the store, baseball has its big stars that generate most of the production (Albert Pujols), players that don't contribute much (AAAA journeymen) or players that actually sap production (Jose Guillen).  The Pareto Principle is applicable to baseball as with many other aspects of our lives.