The hell?? Isn't it obvious, HK is a small territory bordering a developing country of more then 1 billion people, you do the math.
Also, in theory HK still controls its own immigration and China is not allowed to interfere, the only exception the One-Way permit loophole.
I'm not sure what math you are referring to. Show me what math you are referring to.
If your argument is that the PRC government wants to increase the Mainlander presence in Hong Kong, why wouldn't they just get rid of the quota in the One-Way permit or relax the standards (which requires people to wait up to 4 years)?
If the general increase in population is a major issue for Hong Kong in general, why doesn't Hong Kong, which has very loose immigration policies for non-Mainlanders (such that Mainlanders purchase foreign passports to make it easier to immigrate to Hong Kong) just make their immigration policies stricter for foreigners (like they already do for housekeepers from SE Asia)?
If Hong Kong banned all Mainlanders, it would not solve any of these issues, as long as it has a policy of being a tax haven that is welcoming of foreigners and foreign investment. The people are complicit by being in favor of the tax haven status--why would they be interested in paying 30-45% income tax and 7-20% sales tax like the rest of the developed world to support social programs when we can just blame Mainlanders for our problems?