S&P/MIB Index (XMIB)

Index Universe  Oct 24  Comment 
The S&P/MIB ETF will cover the Italian equity universe tracking the S&P/MIB index, which was created by Standard & Poor's and Borsa Italiana and launched earlier this year. An exchange-traded fund based on the S&P/MIB index will...


The S&P/MIB is a market capitalization weighted index derived from the top 40 equities of the Borsa Italiana. It covers over 80% of the local market cap and its sector breakdown aims to mirror the health of the 10-economic sectors of the Italian Stock exchange at Milan[1]. The Index is maintained by a partnership of Standard and Poor's and Borsa Italiana.

Weighting and Calculations

These indices are also called market capitalization weighted indices or the value-weighted indices. They involve the total market capitalization of the companies weighted by their effect on the index, so the larger stocks would make more of a difference to the index as compared to a smaller market cap company. This is also called the free float method. The basic formula for any index is (be it capitalization weighted or any other stock index)[2]:

  • Index level= Σ(Price of stock* Number of shares)*Investable Weight factor/ Index Divisor.

The float-adjusted market capitalization is determined through an Investable Weight Factor (IWF)[3]:

IWF = 100% – Sum of the % of shareholdings held by major shareholders.

The Investable Weight Factor is calculated by determining all long-term shareholders owning 5% or more of the shares outstanding of the specific share class, with the exception of Pension Funds and OICR or Organismi di Investimento Collettivo del Risparmio (i.e. mutual funds and Societa' di Investimento a Capitale Variabile, SICAV). In the case of a legally binding control block (patti di sindacato) with a weight of 5% or more, all the individual shareholders of that block, even with individual stakes less than 5%, will also be excluded from the float.

While one might track this portfolio’s value in dollar terms, it would probably be an unwieldy number – for example, the S&P 500 market value is roughly $11.8 trillion. Rather than deal with ten or more digits, the figure is scaled to a more easily handled number, currently around 1250. Dividing the portfolio market value by a factor, usually called the Index divisor, does the scaling.

Continuity in index values is maintained by adjusting the divisor for all changes in the constituents’ share capital after the base date. This includes additions and deletions to the index, rights issues, share buybacks and issuances, and spin-offs. The divisor’s time series is, in effect, a chronological summary of all changes affecting the base capital of the index. The divisor is adjusted such that the index value at an instant just prior to a change in base capital equals the index value at an instant immediately following that change[4].



  • Company should be financially viable
  • All long term shareholders owning more than 5% of the company are taken into consideration on the IWF.
  • The most liquid stocks, which are representative of their industry sectors are represented
  • All stocks on the Italian stock exchange are eligible for the index.
  • At least 30% of the company's stock should be publicly floated

Sector Breakdown

Sector breakdown for the MIB Index

List of companies

The composition of the MIB Index, as of October 24, 2008[6]:

A2A A2A SPA 0.4218
AL Alleanza Assicurazioni 0.5231
G Assicurazioni Generali SpA 0.9059
ATL Atlantia SpA 0.5168
AGL Autogrill SpA 0.3997
BMPS Banca Monte dei Paschi di Siena SpA 0.5073
PMI Banca Popolare di Milano Scrl 1.0546
BP Banco Popolare - Societa Cooperativa 1.0546
BUL Bulgari SpA 0.5062
BZU Buzzi Unicem 0.4704
ENI ENI S.p.A. (E) 0.5479
ENEL Enel SpA 0.715
F FIAT S.p.A. (F-MI) 0.734
FWB Fastweb 0.1888
FNC Finmeccanica SpA 0.7129
FSA Fondiaria SAI 0.5389
GEO Geox SpA 0.3058
ES Gruppo Editoriale L'Espresso SpA 0.3596
IPG Impregilo SpA 0.7393
ISP Intesa Sanpaolo SpA 0.8004
IT Italcementi SpA 0.3965
LTO Lottomatica SpA 0.4113
LUX Luxottica SPA 0.3174
MS Mediaset SpA 0.6707
MB Mediobanca SpA 0.5737
MED Mediolanum SpA 0.3027
MN Mondadori (Arnoldo) Editore SpA 0.4461
PLT Parmalat SpA 1.0546
PC Pirelli & C. SPA 0.502
PRY Prysmian SpA 0.6148
STM ST Microelectronics NV (Italy) 0.7646
SPM Saipem SPA 0.6022
PG Seat Pagine Gialle SPA 0.522
SRG Snam Rete Gas 0.4472
TI Telecom Italia SPA 0.753
TEN Tenaris 0.4176
TRN Terna SPA 0.6739
UBI UBI Banca ScpA 1.0546
UCG Unicredit SpA 0.9038
UNI Unipol Gruppo Finanziario SpA - Ordinary Shares 0.5199


  1. S&P Factsheet
  2. Capitlization method methodology
  3. MIB Methodology
  4. Capitalization Weighted Description
  5. S&P Factsheet
  6. S&P/MIB Index composition
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