I think we should address 2 questions first before we can answer this. Why do some programmers think they are 10x or 100x more productive than others? Is it a myth or is it for real? Give some concrete examples of 10x productivity for a start.
There are not many concrete quantitative statements one can make about the profession, but this is one of them.
To the extent to which coding on a whiteboard is an indicator of real-world productivity, there definitely seems to be at least 5x difference.
In those cases, I was seeing at least a 10x productivity increase because while they were sitting around thinking about the problem, I was already writing code, working on the parts that I did understand, while gaining a greater understanding of the rest during that process. Once we all reached the point of understanding, those gains became negligible, and our productivity was probably closer to par.
If you're writing the same old boilerplate code day in, day out, it is probably hard to realize increased productivity between individuals. However, if you're venturing into new problems constantly, I believe different developers can be quite a bit more productive over others.
For example: How many more tasks did you complete on average? How much time did you require the assistance of your colleagues? How many times per day do you interrupt other developers and prevent them from doing their job?
So the productivity multiplier is either over 1x or under 1x. When you multiply it up together for all the members of your team, and you normalize so that the lowest multiplier is 1x, you might realize that in fact some co-workers can be 100x more productive than others.