Only white people for market surveys, please

Upon crossing a border into Hong Kong, there are often staff taking surveys of tourists. They are very professional with PDA's and short, to-the-point questions. However, they seem to only ask foreign (white) tourists questions. I am almost always accosted to reply to their questions. And, I have often seen these survey takers only asking other white people (often there are only a few white people crossing the border with me in a sea of Chinese). My concern is that these surveys are thus unrepresentative.

Perhaps the ethnic Chinese are unwilling to answer these survey takers? Or are rude?