Published two years ago, The 4-Hour Workweek, by Timothy Ferriss, is still on The New York Times list of Business Best Sellers (as of 5/3/09). So if you’re working more than four hours a week—or a lot more than that—you may want to read or re-read this book, subtitled, Escape 9-5, Live Anywhere, and Join the New Rich.

As you might expect, Ferriss is a strong believer in the 80/20 Principle, a/k/a the 80/20 Rule or Pareto’s Law. As noted in The 4-Hour Workweek, “Vilfredo Pareto was a wily and controversial economist-cum-sociologist who lived from 1848 to 1923. An engineer by training, he started his varied career managing coal mines and later (became) chair of political economy at the University of Lausanne in Switzerland....The mathematical formula he used to demonstrate a grossly uneven but predictable distribution of wealth in society—80% of the wealth and income was produced and possessed by 20% of the population—also applied outside of economics. Indeed, it could be found almost anywhere.”

Ferris had been working 15-hour days, seven days a week, running his dietary supplement company, and feeling overwhelmed and helpless. After he came across Pareto’s work, he asked himself: “Which 20% of my sources are causing 80% of my problems and unhappiness? Which 20% of my sources are resulting in 80% of my desired outcomes and happiness?” After answering the questions, he stopped contacting 95% of his customers and fired 2%, leaving him with the top 3% of producers to profile and duplicate. He went from chasing and appeasing 120 customers to simply receiving large orders from eight. His monthly income went from $30,000 to $60,000 in four weeks, and his weekly hours dropped to 15, and later to four.