Population Division Technical Paper No. 2020/01 September 2020 Data and methods for the production of national population estimates: An overview and analysis of available metadata* Thomas Spoorenberg** Abstract Official population estimates can be produced using a variety of data sources and methods. These range from the direct extraction of information from continuously updated population registers to procedures for updating the status of a population enumerated previously in a periodic census. Additional sources and techniques involve the use of sample surveys or complementary sources of headcount statistics for specific age groups (e.g., immunization records, school enrollment statistics, electoral roll data). In all cases, the objective is to derive regular (typically annual) time series of the estimated size of a population classified by age and sex. Some methods and data sources are considered preferable, as they are more likely to produce internally consistent and reliable estimates. In all cases, the data and methods used to produce population estimates should be clearly documented and made readily available to data users. These metadata are essential for interpreting properly and for assessing the accuracy and reliability of population estimates and their suitability for informing policy formulation and implementation at the national level. Access to such metadata is especially important if population estimates are being used for comparative purposes at the global level. This paper offers a concise review of the methods that are commonly used by national statistical offices to produce annual time series of population estimates by age and sex. These methods depend on the availability of two essential components: an initial population count and a method of time adjustment. Both components play a crucial role in determining the overall quality of a set of population estimates. The paper formulates specific recommendations concerning best practices for the production of official population estimates. Drawing on information from various sources used by the United Nations to produce its biennial edition of global population estimates, the World Population Prospects, the paper also provides (in the appendix) an overview of data availability and current practices in the production of official population estimates around the world. Keywords: Official statistics, population estimates, data quality, data availability, metadata Sustainable Development Goals: 16, 17 * The current version benefits from the inputs and feedback from Patrick Gerland, François Pelletier, Frank Swiaczny, and John Wilmoth. A special acknowledgment is made to the contribution of Minja Chen in recoding and analyzing the metadata information provided to the Statistics Division of UN DESA. ** Population Division, United Nations Department of Economic and Social Affairs This publication has been issued without formal editing. The views expressed in the paper do not imply the expression of any opinion on the part of the United Nations Secretariat. CONTENTS 1. INTRODUCTION ...................................................................................................................................... 3 2. GENERAL PRINCIPLES ........................................................................................................................... 5 3. FACTORS AFFECTING THE QUALITY OF THE INITIAL POPULATION COUNT AND TIME ADJUSTMENT ..... 8 4. METHODS OF ESTIMATION .................................................................................................................. 11 5. TRANSPARENCY AND AVAILABILITY OF INFORMATION ...................................................................... 17 6. RECOMMENDATIONS ........................................................................................................................... 18 REFERENCES ............................................................................................................................................... 20 APPENDIX .................................................................................................................................................... 22 The Population Division of the Department of Suggested citation: Spoorenberg, Thomas (2020). Economic and Social Affairs provides the Data and methods for the production of national international community with timely and accessible population estimates: An overview and analysis of population data and analysis of population trends and available metadata. United Nations, Department of development outcomes. The Division undertakes Economics and Social Affairs, Population Division, studies of population size and characteristics and of Technical Paper No. 1. the three components of population change (fertility, This technical paper is available in electronic format mortality and migration). on the Division’s website at www.unpopulation.org. The purpose of the Technical Paper series is to For further information, please contact the Population publish substantive and methodological research on Division, Department of Economic and Social Affairs, population issues carried out by experts both within Two United Nations Plaza, DC2-1950, New York, and outside the United Nations system. The series 10017, USA; phone: +1 212-963-3209; e-mail: promotes scientific understanding of population [email protected]. issues among Governments, national and international Copyright © United Nations, 2020. organizations, research institutions and individuals engaged in social and economic planning, research Figures and tables can be reproduced under a Creative and training. Commons license (CC BY 3.0) http://creativecommons.org/licenses/by/3.0/igo/ 1. INTRODUCTION High-quality, transparent information is needed to support and inform public policy formulation and decision-making. Providing information in an objective, transparent and independent manner is therefore important to achieve and maintain public trust in official statistics. Obtaining accurate and reliable information about a country’s population is important not only to determine its size and understand other characteristics such as age, sex, residence, education, labor force status, occupation and other attributes, but is useful as well for policy formulation and evidence-based decision-making and to monitor progress towards achieving the universally recognized and internationally adopted Sustainable Development Goals (SDGs). While all these characteristics are important, determining accurately the size and structure of the total population is essential, because it affects the accuracy of many, if not all, of the other variables (Commission on Population and Development, 2016a, 2016b). Therefore, it is imperative that the estimation of the size and composition by age and sex of a country’s population be conducted with standard/agreed upon procedures. Global efforts have been pursued to guarantee that official information released by statistical organizations meet minimum quality standards (UNSD, 2019a). In the area of the production of official population estimates,1 several guidelines are available since the 1950s (United Nations, 1952, 1955, 1956) with more specific principles and recommendations for censuses and vital registration that have been revised over time (UNSD, 2014, 2017, 2019b). The compliance to these best practices is recommended, especially if official data are to be used for international comparative purpose. It is therefore important that countries follow standards in producing official estimates and in providing sufficient metadata about those estimates. At the international level, the United Nations Statistics Division (UNSD) is responsible for collecting, organizing and disseminating official population statistics. Official population estimates are collected by UNSD through annual questionnaires sent to national statistics offices. The collected data are published in the Demographic Yearbook collection on an annual basis.2 In addition to numerical population figures, UNSD gathers also metadata documenting the methods used by countries in constructing their latest population estimate. Such data allow us to draw several conclusions about the global situation in terms of data availability, estimates by period, and the methods used to produce official population estimates. In addition, such information is very useful to assess the reliability of the estimates made available by national statistics offices. UNSD (2018a: 51) defines as reliable data estimates that “are based on a complete census (or a sample survey) and have been adjusted by a continuous population register or on the basis of the calculated balance of births, deaths and migration.” When producing its biennial collection of population estimates and projections for successive revisions of the World Population Prospects, 3 the Population Division of the United Nations Department of Economic and Social Affairs utilizes various types of data sources, such as population censuses, civil registration data, population registers and sample surveys, as well as official population estimates. In the 1 “Official population estimates” will be used herein to refer to the official statistics pertaining to the size and structure by age and sex of the population that are produced by national governmental institutions (usually the national statistics office). 2 https://unstats.un.org/unsd/demographic-social/products/dyb (last accessed 20 February 2020). 3 https://population.un.org/wpp/ (last accessed