Follow-up to Tim Ferriss Post

John left a comment on my previous post about Tim Ferriss's post (Thanks, John!). I agree with John that we can certainly find activities where you will not be a world-class performer after a year's immersion. On the other hand, I do have a couple of nuances to add to the original post:

• The issue of relative versus absolute improvement: When we talk about "world-class" performance, we have a certain absolute standard in mind (whether or not such a thing exists out there!). We can certainly name many fields where you will not be able to ascend to those levels. OTOH, if you did spend a year of immersion into any field, you will most definitely improve your performance relative to where you were when you started. I do not see any holes in that statement; do you? For all practical purposes this is what we typically seek - to be significantly better at something. No? (I want to be a really good roller skater, for example. I do not particularly care about becoming world-class.)
• How good do you have to be to be called "world-class"? I am talking about quantification here. Top 10%? 5%? 1%? 0.1%? Obviously this is an arbitrary cut-off. I do not think it is logical (or fair) to equate being "world-class" with being a "star". At a given point there will be only one tennis champ, but there will be a much larger number of world-class players.
• Another question to think about: are there certain fields where it is possible and others where it is not? In other words, is there a taxonomy of fields along the "possibility of becoming world-class in one year of immersion" dimension? In competitive sports there is usually a ranking available so it will be generally possible to quantify world-class, howsoever you define it. On the other hand whom do you call a world-class computer programmer?