I read an interesting article by RSS spreading communal hatred and distrust among Indians. One of the major points it re-emphasized was that Muslim population was expanding because they are allowed to have multiple marriages.
As a proof they showed the census data proving that Muslims grew by an alarming 40% in the last decade. What it forgot to include was that in the last census, the population of J&K, and Assam (both Muslim predominant states) was not taken into account. Point is if your base data is faulty, then you cannot arrive at any conclusion.
My question is, how many of the Muslim friends you know actually have multiple wives? (Hardly 2-3percent have 2 wives and rarely you will find more than that. In fact which female would like to go in such a relationship?)
Even if they do have multiple wives, the reproducing capacity of a female does not change with monogamy/polygamy. On the contrary, having larger number of adults to feed induces liabilities and hence reduces the economic level of the members.
So in a traditional monogamous Hindu family having 2-3 children is common, it is highly absurd to even think of a Muslim male to support 5 wives and 10-15 offspring. I will be in fact welcome you if share if you have ever come across such an incident.
What RSS failed to comment about was the new Draupti like families that are emerging in UP, Haryana. Due to smaller lands ownership and falling male-female ratio 4-5 brothers are sharing single wife. Unlike polygamy, polyandry drastically increases the population. The female in such a relation is seen as a production line popping one baby after another.