AIB shares closed at 18.74 after Friday's trading, putting the bank's market capitalisation at just below 16.5bn. It now stands behind Schneider Electric, a French electricity management company and a noncomponent of the index, for the last available Euro Stoxx slot.

The selection list for the index will be published tomorrow. The Euro Stoxx 50 rebalances on 21 September, at which point AIB will officially leave the blue-chip cohort.

The bank had been hovering beyond the cut-off point since June, when it slipped to 52nd position. Under Dow Jones Euro Stoxx rules, the top 40 stocks based on free float market capitalisation are automatically included in the index. After that, any current components of the index ranked between 41 and 60 are added, followed by non-components if necessary, until the remaining 10 places are filled. Schneider benefited from a 4% boost in its share price Friday as the market anticipated its inclusion in the last available place.

Being a part of the Euro Stoxx index can boost the price of a stock as participation makes the shares available to index-linked investments such as exchange traded funds.

AIB enjoyed a near 6% price boost in the weeks leading up its 1 July 2005 admission to the Euro Stoxx 50, as investors anticipated future prices rises above its 17- 18 range at the time.

AIB traded as high as 24 in February, but has lost nearly a quarter of its top value since then as the Irish housing slowdown and the broader market difficulties have taken the shine off bank stocks. The Iseq has been the developed world's worst performing index this year.

Brokers have been reluctant to predict how much further AIB will fall once it exits the Euro Stoxx index, but unanimously believe the change at the very least represents a negative technical factor. AIB's fundamentals remain strong, however, according to analysts.