Dear Dawa, Adding to your reply... if u take the latest survey given by govt of india. it is not Mulim community with the most number of more than one wife... but the Hindus you know the term (Patri Vivah).
Also, in muslim community... one can not just marry 4 women... there are some very-2 important rules to follow. If you read those rules , you will come to know that marrying more than one woman is a PROVISION and not the requirement. I also want to comment that there are some bad muslims (as in every community) who use this provision for wrong reason, means they are committing sin.