I have not seen Armstrong cover that, but 80/20 is everywhere.....
http://www.armstrongeconomics.com/research/economic-thought/by-author/pareto-vilfredo-f-d
To add to the subject, (mainly because I'm the one who brought it up)
Quote
13 Examples Of The Pareto Principle
posted by Anna Mar, Simplicable, May 30, 2013
In 1906, Italian economist Vilfredo Pareto noted that 80% of Italy's land was owned by 20% of the people.
He became somewhat obsessed with this ratio, seeing it in everything. For example, he observed that 80% of the peas in his garden came from 20% of his pea plants.
The 80:20 ratio of cause-to-effect became known as the Pareto Principle.
posted by Anna Mar, Simplicable, May 30, 2013
In 1906, Italian economist Vilfredo Pareto noted that 80% of Italy's land was owned by 20% of the people.
He became somewhat obsessed with this ratio, seeing it in everything. For example, he observed that 80% of the peas in his garden came from 20% of his pea plants.
The 80:20 ratio of cause-to-effect became known as the Pareto Principle.
http://management.simplicable.com/management/new/examples-of-the-pareto-principle