Big changes in the shape and size of many Dáil constituencies have changed the electoral map of Ireland since the last general election.

The number of Dáil seats has been cut from 166 to 158 and the number of constituencies from 43 to 40.

The constituency commission which reported in 2012 was given the task of reducing the membership of the Dáil from 166 seats to a figure in the range of 153 to 160.

It ultimately decided that 158 seats was the most appropriate number to meet the constitutional population to Dáil deputy requirement set down by the Constitution.

In the process a number of long established three-seat constituencies were consolidated into larger county based five-seaters while there were significant changes affecting all of the Dublin constituencies.

Most of the existing constituencies have been changed to a greater or lesser degree. There are now 11 five-seat constituencies, 16 four-seaters and 13 three-seaters.

In Dublin the biggest change involved the amalgamation of the old three seat constituencies of North Central and North East into one five-seater called Dublin Bay North. It stretches along the coast from Clontarf to Baldoyle and Howth and inland to Donnycarney and Darndale.

On the other side of the Liffey the old Dublin South East has been expanded and renamed Dublin Bay South. To its traditional heartland of Sandymount, Ringsend and Ranelagh has been added a big chunk of Terenure and Kimmage.

The neighbouring Dublin South Central which stretches from Kilmainham and Ballyfermot out to Walkinstown has been reduced from a five to a four-seater.

Dublin Central based around the north inner city has been reduced from a four to a three-seat constituency and has lost a large slice of territory to West and North-West.

The ever fluid borders of Dun Laoghaire have expanded again to take in parts of Stillorgan, Leopardstown, Foxrock, Cabinteeley and Carrickmines which it lost to Dublin Rathdown, formerly Dublin South, in the last review. It remains a four-seater.

Dublin South, which was a five-seater since 1981, has been savagely truncated. As well losing some territory to Dun Laoghaire it has lost a huge swathe of Rathfarnham, Ballyboden, Knocklyon and Firhouse to Dublin South West.

South West centred on Tallaght has been expanded from a four to a five-seater with the addition of such a big chunk of middle class housing changing the social mix quite significantly.

Dublin Mid West remains a four-seater based on the Clondalkin and Lucan areas and the boundary is unchanged.

Dublin West has lost a swathe of territory on its northern border and gained some from Dublin Central. The three-seat Dublin North West centred on Finglas and Ballymun is largely unchanged but the addition of Glasnevin and Drumcondra has altered the demographic profile of the constituency.

North county Dublin has undergone extensive changes gaining an extra seat to become a five-seater along with a big chunk of territory around Swords and Portmarnock coming back in and is now called Dublin Fingal.

In the rest of Leinster the only big change is that the old five-seat Laois-Offaly constituency has been split in two with each county now a three-seater. The new Laois constituency takes in part of south Kildare while Offaly gets a chunk of north Tipperary.

Meath East and West remain the same as do Louth, Wicklow, Wexford and Carlow Kilkenny. There are some minor changes in Kildare North and South.

Cavan-Monaghan has been reduced from a five to a four seater and in the process has lost a sizeable portion of west Cavan to the newly reconstituted four-seat Sligo-Leitrim. A portion of south Donegal has also been included in this constituency which has brought Leitrim back into its traditional embrace with Sligo.

Donegal is now one five-seater instead of two three seaters while the Taoiseach's home base of Mayo has lost a seat to become a four-seater. A portion of south Mayo has gone into the five-seat Galway West.

The other big change in the region is that Galway East has lost a seat and is now a three seater and it has also lost a substantial portion of its territory to the new constituency of Roscommon-Galway.

There are also extensive changes in Munster. Cork South-Central loses one of its five seats with a portion of its old territory going into Cork North-Central which remains a four-seater.

The four Cork county constituencies are largely unchanged as is Waterford and Clare but there are significant changes in County Limerick. Limerick City remains a four seater but expands to take in a lot of the old Limerick East. Limerick county remains a three seater taking back a slice of territory that was part of the old West Limerick-Kerry North.

There are dramatic changes in the neighbouring county of Tipperary where two long established three seaters have been merged to form one five seat constituency. The northern fringe of the county has been hived off into Offaly.

The same thing has happened in Kerry where two three seaters have been stuck together to make one large five-seat constituency.

The overall reduction in the number of seats and the boundary changes have made the outcome of the election even more difficult to call than usual.