In short: becoming world-class is getting to the top N percent and depends on the number of people willing to practice for being world-class. It seems that cur

In short: becoming world-class is getting to the top N percent and depends on the number of people willing to practice for being world-class. It seems that currently we've settled to 10 000 hours because 10 000 hours seems to reduce the number of candidates enough to make each "survivor" a real expert. If suddenly more people started to practice 10 000 hours, you would possibly need 15 000 hours to distinguish yourself back to the top N percent among the horde of damn good (by our current standards) piano players, programmers, or whatever. Being world-class also depends on the subject: the world can take only so many world-class piano players because the audience is somewhat limited, but it can absorb many more programmers because there are roughly infinite number of interesting and useful project to be done.