The over 65s have already made their presence felt in this general election by torpedoing plans to increase the minimum State pension age. And on Saturday they are set to have a bigger influence than in previous ballots - due to sheer numbers.

In 38 of the 39 constituencies, there has been an increase in the number of people aged over 65, data from the Central Statistics Office shows. The exception is Dublin North West.

The constituency of Kildare South has seen the largest increase in over 65s in the State since 2011. The population cohort has more than doubled (53 per cent) from 7,892 in 2011 to an estimated 12,061 today in the constituency, which includes the towns of Newbridge, Kildare and Athy.

The constituency has also seen the largest population increase as whole since 2011 at 31 per cent from 87,776 to 114,810. This is in part due to a boundary change, with the constituency expanding in size since 2011 and Kildare South now has areas to the west of Monasterevin and north east of Edenderry. A number of constituencies have had their boundaries re-drawn since 2017 while retaining the same constituency name and this Irish Times analysis has been carried out on CSO constituency data from 2011 and the redrawn 2017 constituencies based on 2016 data. The figures can be seen as indicative of a broader demographic pattern.

Across the State, the number of people aged over 65 has risen by almost one fifth (19 per cent) since 2011, the largest increase in any of age group category analysed. This is primarily due to declining death rates.

In contrast, the population of under 35s is down 10 per cent in the same period.

After Kildare South, the constituencies with the highest increase in over 65s are Cavan-Monaghan (41 per cent), Dublin Mid-West (40 per cent) and Dublin Central (39 per cent). These constituencies have had their boundaries re-drawn since 2011 which also accounts for some of the population change. Dublin Central has had areas around Drumcondra/Glasnevin added and Cavan/Monaghan has had areas south of Kingscourt and west of Cavan town added.

In Dublin North West, the only constituency which bucked the trend, there has been a decrease in the over 65s population of 7 per cent since 2011.

This pattern could have an important influence on marginal seats, given Irish Times opinion polls during the campaign show older people more favourable towards Fianna Fáil, while among the under 40s the most supported party was Sinn Féin.

Under 35s

Most constituencies have seen a decrease in the under-35 voting age population (18-34). The three constituencies with the biggest decline in this age group are all in Connacht with Sligo-Leitrim decreasing by 20 per cent, Galway East by 18 per cent and Galway West by 17 per cent.

According to statisticians, the decline is attributable to falling birth rates in the late 1980s and early 1990s as well as emigration trends since 2010 which saw many young people leave the country to find employment.

Dublin Central and Cavan-Monaghan are the constituencies with the largest population increase in under 35s at 16 per cent respectively. Only two other constituencies saw an increase in this age group: Kildare South at 11 per cent and Cork North Central at 1 per cent.

In Dublin, several constituencies have seen significant decreases with Dublin West, Dublin South West, Fingal and Dublin Mid-West seeing the under 35s population falling by 12 per cent, while Dublin North West has seen a 15 per cent decrease.

The under 35s make up 22 per cent of the population and 29 per cent of those eligible to vote at the weekend.

The most recent Irish Times/Ipsos MRBI poll this week showed that if 18-24 year olds only had a vote, Sinn Féin would top the poll at 27 per cent, followed by Fianna Fáil (20 per cent), Independents/Others (19 per cent), Fine Gael (17 per cent) and the Green Party (7 per cent).

35-49

In the 35-49 age bracket, the population has increased 7 per cent nationally and most constituencies have seen an increase in population with the most significant being in Dublin Central (41 per cent); Kildare South (34 per cent); Cavan-Monaghan (23 per cent); Dublin West (20 per cent) and Dublin Mid-West at 16 per cent.

Sligo-Leitrim is the only constituency to see a decrease in this age category with a 4 per cent drop in population since 2011. Nationally the population of 35-49 year olds has increased 7 per cent.

The 35-49 year old age group makes up 23 per cent of the population and 30 per cent of those eligible to vote.

The last Irish Times/Ipsos MRBI poll showed increase in support for Sinn Féin was largely driven by voters aged 35-49 and Dublin voters. For Fine Gael, the most significant decline in preference for the party was recorded among 35-49 year olds (from 29 per cent to 18 per cent).

50-64

For the 50-64 age group, the most notable increases are again largely Leinster-based. This population group has seen its size increase by one-tenth since 2011 with Kildare South (43 per cent) having the largest increase among this age group also.

This is followed by Dublin Central (41 per cent); Cavan-Monaghan (27 per cent); Dublin Fingal (16 per cent) and Dublin West (16 per cent). The 50-64-year-old age group make up 17 per cent of the population and 22 per cent of those eligible to vote.

In the poll conducted earlier this week, Fianna Fáil remained the most popular party among the voters aged 50 or over, on 29 per cent.