Madagascar began its third population and housing census on Friday, an exercise that will last three weeks.
The statistics agency, Institut National de la Statistique (Instat), boss Ida Clément Rajaonera said some 40,000 census agents had been recruited.
The General Census of Population and Housing (RGPH III) will be conducted until June 10 with results expected at the end of the year.
The last census was carried out in 1993, after an initial one in 1975.
Attempts to conduct a population survey in 2003 were unsuccessful due to political instability.
The exercise was then scheduled for August 2009 but failed again following months of bloody protests and ousting of President Marc Ravalomanana.
Plans to carry out the census resumed after current President Hery Rajaonarimampianina took over in 2014.
The exercise will cost $26 million and is funded by the World Bank, the European Union and the United States.
The United Nations Development Programme (UNDP) and the United Nations Population Fund (UNFPA) have also provided financial and technical support.
The latest data on Instat's website estimates the Malagasy population to be between 22-26 million.
The 1993 census showed that there were 12,238,914 people with 50.3 per cent of them women and 49.7 per cent men.
UN recommends conducting a census of the population once every 10 years.