So, I think you're confusing 'probability' with 'cardinality of the set of successful outcomes' (let's call that k). If k is proportional to the size of the com

So, I think you're confusing 'probability' with 'cardinality of the set of successful outcomes' (let's call that k). If k is proportional to the size of the company (n, say), then you are absolutely right that k/n (i.e. the probability) will not change as n changes. But the statement actually says that the _probability_ is proportional to n, not k. So no, the probability is not constant. The idea of the probability being directly proportional to n is not technically correct for other reasons (with large enough n, this would allow for probabilities larger than 1), but not for the reasons you're mentioning here. Perhaps more importantly, the meaning of the comment is independent from this pedantry and should be interpreted less literally so we can focus on its actual meaning.