Pareto principle is named after the Italian economist Vilfredo Pareto. He devised a mathematical formula to explain the unequal distribution of wealth in his country, that only 20% of the people owned 80% of the wealth. Read more at: (
http://management.about.com/cs/gener...reto081202.htm)
This tool has long been recognised as an effective management tool to understand things in a better perspective. 'Vital few and trivial many' is another attempt at describing this principle.
It is applied to a variety of situations in practice. The essence being, that 80% of the results are achieved by 20% of the efforts. And this is relevant for us as well.
Although it may tend to give an oversimplified view of CSS. But, this is what the purpose of the study plan is, to channel our efforts to the key areas (20%) of syllabus for each subject.