I believe that Artisans are ~40% of the general population.
And keep in mind that Artisans are also known as Dionysians (using the Kiersey-Bates system of nomenclature) ... which means that most of them probably don't have the desire or patience to sit down and answer a bunch of questions ;-)
The respondents to this test were self-selected, which means we ended up with lots and lots of Introverts (who are only ~25% of the population) because Introverts enjoy this kind of thing ... and relatively few Extroverts and Dionysians/Artisans (who are each a pretty large segment of the population, ~75% and ~40 respectively) who DON'T generally enjoy this kind of thing ;-)
Excellent breakdown. You're absolutely right. I should have thought of that.