In The 4-Hour Body: An Uncommon Guide to Rapid Fat-Loss, Incredible Sex, and Becoming Superhuman author Timothy Ferriss says,
To be perceived as fluent in conversational Spanish, for example, you need an active vocabulary of approximately 2,500 high-frequency words. This will allow you to comprehend more than 95% of all conversation. To get to 98% comprehension would require at least five years of practice instead of five months. Doing the math, 2,500 words is a mere 2.5% of the estimated 100,000 words in the Spanish language.
1. 2.5% of the total subject matter provides 95% of the desired results.
2. This same 2.5% provides just 3% less benefit than putting in 12 times as much effort.
This incredibly valuable 2.5% is the key, the Archimedes lever, for those who want the best results in the least time. The trick is finding that 2.5%.
Where else does this apply? Is there a 2.5% of Jiu Jitsu that will handle 95% of the situations you end up in on the mats?
I believe there is, but like he said the trick is finding that 2.5%.