comparative advantage in southern africa custom union. Look into current
statistics and revenue allocation

What you have asked isn't even a question. Could you try a little
harder when phrasing it?

I will assume you are asking about customs unions, and I will contrast
this to a free trade bloc.

A customs union is where nations can trade freely with one another,
but may have their own tariff rates. A free trade bloc has free trade,
but has one common tariff for the whole bloc.

A customs union is politically easy, but an administrative nightmare.
Nations simply sign, and the union is born. But if country A has a 50%
external tariff, and B has a 2% external tariff, what is to stop firms
from importing into B, and transporting into A? In order to maintain
the 50% tariff rate, border patrols must exist. But there are further
complications. What if some of a good in B was produced locally, and
the rest produced outside the union? When does a locally produced good
stop being a locally produced good?

A free trade bloc is much simpler. Internally, there is no barrier.
Externally, the tariff barrier is the same. So it doesn't matter if a
good is imported into A or B, there is no incentive for taxation
arbitrage. However, it is politically difficuly because of the
surrender of national sovereignty to a supernational body, the trade
bloc.

Unfortunately, your question mentions only South Africa, which can't
form either a customs union or a free trade bloc with itself. Do you
mean the rest of Africa? As I understand it, very few statistics are
available for what occurs in Africa.

Please be more specific.

Thank you for your response. please look at the question again. I have
asked about the southern africa custom  union: how does not the law of
comparative advantage explain the trade relation. please note that the
southern africa custom union is made up of south africa, lesotho,
botswna, zimbabwe and swaziland.
thank you.