Home > Business Databases, News & Feedback > Indices, constituent lists and weightings

Indices, constituent lists and weightings

It is relatively easy to find the constituents of an index, such as the FTSE 100 or  S&P 500, but more difficult to find the details of the weightings that are used.

  • Bloomberg – search for the index and use the MEMB (member) function.
  • Datastream – search for the index and find the corresponding constitents list, or search directly for the constituents list (see screenshot below)
  • online – some index providers provide the current constituents of their most popular indices

BloombergOnly Bloomberg (MEMB) provides the detailed weightings of the shares/stocks in an index, and this is not for all indices. In particular, there is no detail available on the weightings of the S&P 500 constituents – more detail below.  (It appears that S&P (Standard & Poors’) guard this information carefully and you need a premier subscription with them to get it.)

Datastream Navigator screenshot

Datastream Navigator Equity Index Search

S&P 500 constituent weightings

Although S&P publish some detail of how the S&P 500, and other indices, are constructed this is not sufficient to calculate the weightings. The companies in the S&P 500 are weighted by market capitalisation, but this is free-float adjusted so that only stocks available for trading are included. In addition, there are rules about the trading history required before a stock can be included in the index, and the handling of mergers and acquisitions.

And finally

Did you know –  the FTSE 100 currently consists of 100 companies but 102 shares. There are 2 companies each with 2 distinct shares: Royal Dutch Shell A,  Royal Dutch Shell B and Schroders, Schroders N/V

Thanks to Jan Novotny whose seemingly simple query, “Do we have a database that gives the constituent weights of the S&P 500?” prompted an investigation and this post.

  1. 6 August 2012 at 6:28 pm

    You might want to consider SPY’s weighted holdings as a proxy for the S&P 500 weightings.


  2. Robert
    1 September 2015 at 4:50 pm

    I don’t see how you get the weights for the FTSE from the constituent lists. Can you provide more details?

    • Mark Greenwood
      9 September 2015 at 10:37 pm

      You are right – you can’t get the weights from the constituent lists. You have to use a service like Bloomberg that gives the weights.
      You can estimate from the market capitalisation of the constituents but the actual weighting rules are not, to the best of my knowledge, public.

      • Robert
        9 September 2015 at 10:41 pm

        That’s what I was afraid of. Still, getting the constituent lists is nice. Thanks!

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