FTSe Spread Betting http://www.financial-spread-betting.com/Spread-betting-ftse-dow.html What are the main weightings behind the FTSE 100 index. David Jones of IG responds. There are lots of things that influence the FTSE 100 in the UK; to start with there are clearly the shares that make up the index and there is more of a weighting of the index in certain sectors. In 2011, the mining (Rio Tinto BHP Hilliton and banking sectors (Barclays, LLoyds...etc)