The Government today urged the public to play its part in ensuring Sunday's 2006 census is a success.
Chief Whip Tom Kitt called for a repeat of the traditional positive response to ensure the information provided is as comprehensive as possible.
"This is a particularly crucial census, taking place at a time of unprecedented demographic and social change in Ireland," he said. "It is possible that the population could be as high as 4.2 million which would be the highest since 1871, 135 years ago.
"In recent years we are all aware of a much changing Ireland, an Ireland that has seen a huge influx of non-Irish nationals which has created a new, vibrant, multicultural society," Mr Kitt said.
"For the first time, the census will give us precise figures on the numbers of non-Irish nationals living and working here."
Mr Kitt said the information provided by those filling out census forms would determine where essential services would be provided.
"At both national and local level, population statistics are essential for planning the provision of essential services such as health care and education and will also advise on employment trends," he said.
"In addition the census will inform us as to other more local needs such as retail outlets and social amenities. The results will greatly help the Government with special strategic planning."
Mr Kitt insisted all information collected would remain private, pointing out that this confidentiality is guaranteed by law. He also paid tribute to workers in the Central Statistics Office and the 5,000 field staff.
A translation of the census form is available in 11 other languages as well as Irish and English. The form is also available in large print and Braille, and an audio version for visually impaired has also been produced.