Quote from cashonly:
It's more to create indices of specific sub-industries that don't already have an index. For example an athletic shoes IDX would have NKE, RBK, FL, and some others.
I see. I don't think your will get a clear advice with what weighting to go ; its really up to you. You also must have an upfront rules how to handle future additions/delisting ( and this is not so easy as its sounds). Here are some scenarios :
1. Buyouts and mergers
2. Add new
3. Delete existing
4. Dividends ( for total return)
BTW , never heard of volume weighting.