The need to know the available resources – primarily the human capital – has been recognized by rulers since the dawn of organized societies. Counting the people and other stock-taking, known as a “census”, dates back five thousand years. 1

Population censuses, in the modern meaning of the term, were introduced largely in 17 th century in countries all over the world. Since these times until today, censuses represent a unique and powerful tool to quantify population, social and economic phenomena and to provide invaluable understanding on the structure and capacity of each village, town and neighborhood. At the same time, preparing and conducting a census provided innumerable generations of statisticians an exceptional learning opportunity and experience. Over time, the census grew into a cornerstone of the national statistical system in terms of providing comprehensive small area statistics, sample frame for launching specialized surveys and anchoring the technological and methodological considerable investment in official statistics every ten years.

Today, census takers face even more pressure than, perhaps, ever before. The need to reduce the overall costs of the census, to implement contemporary methods for data collection, to develop a combination of techniques that would overcome the increasing reluctance of the population at large to provide information on themselves, to introduce and maintain geo-referencing of census statistics and to take full advantage of existing alternative sources for generating small area statistics – such as registers and administrative data – would be just the beginning of a long list of considerations faced by our colleagues all over the world.

Conducting population and housing censuses offers a single most visible opportunity to build the trust into official statistics, as the census collects data on each individual and each housing unit. With raising concerns regarding the confidentiality and perusal of individual data, it is critical to convey to the public the Principle 6 of the Fundamental Principles of Official Statistics – Individual data collected by statistical agencies for statistical compilation, whether they refer to natural or legal persons, are to be strictly confidential and used exclusively for statistical purposes. The importance of this principle is especially valid in terms of contemporary perceptions of exposing individual data to both inside and outside abuse by various data collectors.

The essential approach of a traditional census, canvassing the entire country, knocking on every door and collecting information on everyone, remains relevant for many censuses in this, 2020 Round of Population and Housing Censuses, covering the period 2015–2024. And a substantial number of countries will also implement a combination of methods, involving population and other registers. At the mid-point of this census decade, this issue of the Journal of International Association of Official Statisticians comes remarkably well-timed and in the pages that follow readers will have the opportunity to acquire a comprehensive understanding on where we are in terms of ensuring that all the countries in the world conduct at least one population and housing or produce small area geo-referenced census statistics in the period 2015–2024 and what are national practices and experiences at this point of time.

The need for detailed population statistics is higher than even before, especially in the context of the implementation of the 2030 United Nations Sustainable Development Agenda and, of course, these needs will

continue even after the 2020 round of censuses. Learning from experiences in this round would lay a groundwork for the next one; thus, the volume like this special edition is meant to take a good and hard look at past and contemporary census-taking experiences while at the same time providing a glimpse of the future of census-taking and of the most efficient production of small area census statistics.