I would say that the amount sold with spots is less then 5%. But, a lot of the saddelbacks, half bars, etc. will get small spots so it might be over 5% eventually.
I have 5 loaches and one has 2 spots. Like groovitudedude's but mine has another spot right above the other. So in my tank it's 20% but overall Wurm is probably right on with less than 5%.
Maybe add 'Less than 1%' to the poll. I haven't found even one spotted loach among the hundreds I've seen this year. I think Bret is snapping them all up right off the truck.