Wouldn't different countries have different ways to count this? Does every country try to count them? And in countries which do count, but where prostitution is illegal, wouldn't everyone just say "I'm not a prostitute"?
Prostitution is either legal or tolerated in all the above countries so it wouldn't be very hard to have an estimate of how many people were involved in the practice. The polling method used was how many sex workers out of 10000 people.
Little doubtful about these statistics and I agree with Jerry. Prostitution legal and tolerated in the Philippines? Hardly. It's prevalent there and depending on how you count I bet the figure could be significantly higher than 0.85% actually. Some for South Korea. But there are usually no good statistics about these sorts of things. If you count all the girls on Mamba freelancing I'm sure Ukraine and Russia would make the list, as well. Putin bragged about having the best prostitutes in the world.
The percentages are not exact but they are an approximation. In the Philippines, prostitution is illegal; however it is tolerated. And I doubt that Putin bragging about having the "best prostitutes in the world" has anything to do with the number of sex workers.