Polling company Ipsos Behaviour & Attitudes has blamed the lower than expected election turnout for errors in its Exit Poll, which under-estimated Fianna Fáil and over-estimated Sinn Féin's vote, beyond the margin of error.
The Exit Poll was published at 10pm on Friday when polls closed.
It was commissioned by RTÉ, The Irish Times, TG4 and Trinity College Dublin, and was conducted by Ipsos Behaviour & Attitudes.
The Exit Poll put Fianna Fáil at 19.5%, Sinn Féin on 21.1% and Fine Gael on 21%.
Final vote share for Fianna Fáil was 21.9%, up 2.4% on the poll. Sinn Féin was 19.0%, down 2.1% on the exit poll.
Both those estimates were outside the margin of error of +/-1.4%.
Fine Gael's vote share was 20.8%, down 0.2% on the poll and within the margin of error.
Kieran O'Leary of Ipsos B&A has pointed to the low turnout of 59.7% for skewing the data and affecting its model.
He said there were anecdotal reports of a higher decline in turnout among young voters than among older voters.
He added that it was also possible that the decline was more severe in urban areas than in rural areas.
"This could in turn lead to an over-sampling of younger voters in urban areas, which would inflate support in the poll for parties such as Sinn Féin and Social Democrats and in turn deflate the support in the poll for parties such as Fianna Fáil and Independent Ireland."
Mr O'Leary also said that a potential second factor was the higher level of refusal than previous polls with a notable skew in refusals towards older voters.
Again this could have contributed to the underestimation of Fianna Fáil and the overestimation of Sinn Féin.
5,018 voters were surveyed at 253 polling stations in all constituencies.
Turnout falls below 60%
The national turnout was down to 59.7%, marking the lowest turnout since 1923, the last time the number was below 60%.
It also shows a pattern of decline, with the number dropping in each of the last four elections, which many commentators have said is worrying and could indicate a lack of confidence in the democratic process.
However, that all comes with a note of warning. The turnout percentage is calculated based on the registered number of potential voters, and the Electoral Commission has warned that the accuracy of that register will soon be reassessed.
We need your consent to load this flourish contentWe use flourish to manage extra content that can set cookies on your device and collect data about your activity. Please review their details and accept them to load the content.Manage Preferences
