Nowadays, Hauz Khas is a chic quarter in the south of Delhi, which is popular with wealthy city dwellers. But parts of the area were classified as rural in 2011 when India's last census was carried out. Researchers say that delays in the implementation of the latest national census, which was postponed due to the Covid 19 pandemic in 2021 and has not yet been planned, mean that many important data records are out of date. Without an updated census, scientists say that their analyzes have become unreliable on topics such as population age and urban migration.

"The implementation of the census is now a top priority, otherwise all of our survey data will be questionable," says Pronab sen, chairman of the statistics committee, who will advise the government in Delhi on its statistical surveys.

The census is a treasury of information about the Indian population to the level of individual households. Governments use the data to plan and assign resources, from vaccines to schools to grade. It is also a source of validation for many other surveys and analyzes on economic and health trends.

"If the census is not carried out, it will fundamentally harm Indian social sciences and our ability to understand Indian society," says Aashish Gupta, demograph at the University of Oxford, UK.

a Herculean task

A census for 1.4 billion people is a Herculean task. Before it begins, there is a housing stock with which trained census employees, so -called enumerators, mark every household on one card. They collect details about the type of every residence and the material from which it consists.

The house version forms the basis for the census in which enumerators visit every household and collect details such as age, level of education of each member and whether they belong to a marginalized group. They also record details of amenities in the area, such as drinking water supply and electrification. In order to complete the 2011 census, around 2.7 million enumerators carried out personal interviews with people in 240 million households over several weeks.

The data is then collected and published a few years later. The census of 2021 should be the first to replace the paper -based forms with a mobile app, which could accelerate the process. But in September 2020, the government postponed the census because of the Covid 19 pandemic, and no new date has been set to date. "There was enough time for the census to state," says Guppa.

At the beginning of this year, the office of the General Registrar and Census Commissioner in Delhi, which monitors the census, extended the deadline for freezing the administrative boundaries, which must be done before the census. The extension should be carried out according to the National elections from April to June end.

Natur s Movision team asked the General Registrar and Census Commissioner for a comment on why the census did not take place, but did not receive an answer.

unreliable analyzes

researchers say that they can create reliable forecasts about national trends without current census data, but the estimates are less reliable at regional, national and local level. "We have a fair idea of ​​how many people there are in India, but we have no idea where they are," says sen.

census data also provide information on the sample strategy for more detailed and regular government investigations on births and deaths as well as economic indicators, from unemployment to poverty to consumption, and health indicators, from fertility to child mortality to anemia. Without updated census data, these surveys will not be representative of the population and introduce distortion, researchers say. For example, areas in which the population has grown are underrepresented and areas in which the population has decreased are overrepresented, says Guppa.

"India is a country that depends heavily on surveys", due to its poor quality of the administrative data systems, says demographer K s James, a guest scientist at Tulane University in New Orleans and former director of the International Institute for Population Sciences in Mumbai, which carries out the country's national family survey.

The quality of these surveys based on census data is crucial to understand whether the country has made progress on various indicators- for example whether educational and health policies have bridged the gap for marginalized communities or who have reduced the death rates in young girls who have found the studies higher than young boys. "It's so frustrating," says Reetika Khera, development economist at the Indian Institute of Technology Delhi (IIT Delhi). "Have we made progress in the past ten years?"

Districts find it particularly difficult to examine trends in the birth rate and internal migration, as there have been so many changes in Indian society over the past decade. Since 2011 there has been a rapid country city migration, as well as a mass return of urban migrants to rural areas during pandemic. "It is difficult to say which proportion of the Indian population currently lives in urban areas," says Khera. She estimates that the use of outdated census data means that more than 100 million people in rural areas are excluded from state food subsidies.

researchers also use the census to ensure that their own smaller surveys are representative of the larger population. "We use comparisons with the census to validate our work," says Sonalde Desai, Demographer at the University of Maryland in College Park.

alternative data

Some research groups have searched for alternatives for their surveys. The electoral register created by the electoral commission of India is updated at least every five years before a state or federal election. "It is actually a pretty good sample frame in the absence of the census," says Krishanu Chakraborty, a researcher for public politics and doctoral student at the IIT Delhi. But it is limited to identifying households, not individuals, he says.

chakraborty also evaluates techniques that are based on satellite cards and other geographical information in an area to count buildings and to determine the size and density of a population. But without updated census data, it is difficult to confirm the accuracy of these data records.