PSI-20

It is one of the main national indices of the pan-European stock exchange group Euronext alongside Brussels' BEL20, Paris's CAC 40 and Amsterdam's AEX.

[7] The Portuguese blue-chip market's subsequent performance has broadly followed the trends set by other Western indices, falling in the aftermath of the dot-com bubble before recovering significantly from 2003 onwards.

[9] The number of constituents of the index (20) is below the generally accepted minimum sample size of 30 required to reach statistical significance.

[10] In a move to increase the stability of the index,[11] the review frequency was at this time switched to annually, commencing on the first trading day of March 2008 (in line with the BEL20 and AEX).

[10] Responsibility for the rules and composition of the index rests with an independent PSI Steering Committee,[4] which publishes any decisions a minimum of one month before they become effective.

[12] All listings on the stock exchange which satisfy this criterion are ranked by the total value (in Euros) of shares traded in the previous year (thus taking both market cap and liquidity into consideration), and this classification is used to choose the index's constituents.

Likewise, non-constituents holding positions 19 and/or 20 are not promoted unless a slot in the index is freed up by a constituent falling below 22nd place.

If a newly listed company on Euronext Lisbon possesses a market cap and is predicted to have a liquidity which exceeds that of some existing PSI-20 constituents, then a "Fast Entry" rule can be invoked to insert it into the index.