I have just summarized the 30 components stocks that made up Straits Time Index (STI) and their respective weightage based on the market cap as of 13/04/10.
STI is a market capitalization weighted index and involves the total market capitalization of the companies weighted by their effect on the index. This means that larger stocks would make more of a difference to the index as compared to a smaller market cap company. (E.g. Capitalland (4.04%) will need to move “3 times more” as compared to Singtel (11.49%) in order to shift the STI)
It is always good to know what the respective weightage are for individual company and their effects on STI especially when trading STI ETF.