The Pareto principle, also known as the 80/20 rule, is a theory maintaining that 80 percent of the output from a given situation or system is determined by 20 percent of the input (Bunkley, Nick. 2008) In Pareto's case, he found that roughly 20 percent of the people in his country dominated with 80 percent of the wealth. The principle doesn’t stipulate that all situations will demonstrate that precise ratio – it refers to a typical distribution. More generally, the principle can be interpreted to say that a minority of inputs results in the majority of outputs.
Here are a few examples of the Pareto principle in action (Richard Koch):
• 20 percent of employees produce 80 percent of a company’s results.
• 20 percent of a given employee’s time yields 80 percent of their output.
• 20 percent of a company’s investments produce 80 percent of its investment profits

Pareto's Principle should serve as a reminder to us to stay focused on investing 80 percent of our time and energy on the 20 percent of work that’s really important. It’s not just important to “work hard” and “work smart”, but also to work smart on the right things. In this point I think it is also can link to the knowledge retention.

In an organization, much of vital knowledge can be held by single people. A single subject matter expert may hold vital operational knowledge in his or her head, representing a “single point of failure” for the organization. (In here, we can say this is the 20% of employees produce 80% of a company's results.) If the person leaves, they are older, and they are reaching retirement age. This is a kind of knowledge loss, means when valuable knowledge is no longer available for the organization to use. We want to eliminate the knowledge loss we need to understand the knowledge retention. Knowledge retention in the context of losing key employees and using techniques such as exit interviews to try to capture their knowledge. In reality, knowledge retention should be integrated into how the organization operates and start well before a key employee is about to depart. Although it is considered crucial for long term organizational success, few organizations have formal knowledge retention strategies (Liebowitz 2011).

A knowledge retention strategy as a part of knowledge management (KM) will identify the knowledge resources that are at risk and must be retained, and then implement specific initiatives so as to keep these resources in the firm. Like most other KM-related processes and strategies, success depends upon successful knowledge sharing and having a knowledge sharing & learning organizational culture. For example the burning bridge, this is an emergency situation which occurs when a valuable employee is leaving or is at risk of leaving. (Lecture notes) The knowledge retention toolkit selected for testing that addressed the burning bridge:
 Interviewing (DE Long, 2004), this is a common solution. This tool enabled surviving staff to interview exiting staff to access valuable tacit knowledge using an interview with correct cognitive triggers. If a exiting staff provide some useful knowledge, this tool will be very positive and work to help the surviving staff how to do the job better.
 Mind Maps (Gelb, 1998: 176-177), this is aim to surface tacit knowledge by focusing exiting staff on future thinking. Participants found the tool useful in group environments to surface issues and build connections leading to solutions.
 Videotaping (De Long, 2004). Participants who participated in the filming offered interesting insights into their work history, which contributed to the stock of organizational memory. However, most participants found the idea of videotaping to be intrusive and uncomfortable. Also people may more concerned themselves, for example how they look like in the film rather than how their work. By the way, I think before use those knowledge retention toolkit, we need to understand the pareto principle, 80/20 rule, what is the 20% important knowledge we need to capture.

Bunkley, Nick (March 3, 2008), "Joseph Juran, 103, Pioneer in Quality Control, Dies", New York Times

Living Life the 80/20 Way by Richard Koch