In the study of survey
A census is the procedure of systematically acquiring, recording and calculating information about the members of a given population. This term is used mostly in connection with national population and housing censuses; other common censuses inc ... data
In the pursuit of knowledge, data (; ) is a collection of discrete values that convey information, describing quantity, quality, fact, statistics, other basic units of meaning, or simply sequences of symbols that may be further interprete ...
, microdata is information at the level of individual respondents.
For instance, a national census might collect age, home
An address is a collection of information, presented in a mostly fixed format, used to give the location of a building, apartment, or other structure or a plot of land, generally using political boundaries and street names as references, along ...
Education is a purposeful activity directed at achieving certain aims, such as transmitting knowledge or fostering skills and character traits. These aims may include the development of understanding, rationality, kindness, and honesty. V ...
Employment is a relationship between two parties regulating the provision of paid labour services. Usually based on a contract, one party, the employer, which might be a corporation, a not-for-profit organization, a co-operative, or any ot ...
status, and many other variables, recorded separately for every person who responds; this is microdata.
Survey/census results are most commonly published as aggregates
In geography, regions, otherwise referred to as zones, lands or territories, are areas that are broadly divided by physical characteristics (physical geography), human impact characteristics (human geography), and the interaction of humanity and t ...
The Organisation for Economic Co-operation and Development defines the employment rate as the employment-to-population ratio. This is a statistical ratio that measures the proportion of a country's working age population (statistics are often g ...
), both for privacy reasons and because of the large quantities of data involved; microdata for one census can easily contain millions of records, each with several dozen data items.
However, summarizing results to an aggregate level results in information loss. For instance, if statistics for education and employment are aggregated separately, they cannot be used to explore a relationship between these two variables. Access to microdata allows researchers much more freedom to investigate such interactions and perform detailed analysis.
For this reason, some statistical organizations allow access to microdata for research purposes. Controls are generally imposed to limit the risk that this data may be abused or lead to loss of privacy. For example, the
Integrated Public Use Microdata Series
Integrated Public Use Microdata Series (IPUMS) is the world's largest individual-level population database. IPUMS consists of microdata samples from United States ''(IPUMS-USA)'' and international ''(IPUMS-International)'' census records, as well ...
requires researchers to implement security measures, avoid redistribution of microdata, use microdata only for noncommercial research/education purposes, and not make any attempt to identify the individuals recorded. Names and fine-level geographical data are removed, some data items are altered as necessary to make it impossible to identify individuals, and small ethnic categories are merged.
The International Household Survey Network has developed tools and guidelines to help interested statistical agencies improve their microdata management practices. The Microdata Management Toolkit is a DDI
Metadata is " data that provides information about other data", but not the content of the data, such as the text of a message or the image itself. There are many distinct types of metadata, including:
* Descriptive metadata – the descriptive ...
editor which is now used in about 80 countries, with the support of the Accelerated Data Program, implemented by the
The Partnership in Statistics for Development in the 21st Century, or PARIS21, was established in November 1999 by the United Nations, the European Commission, the Organisation for Economic Co-operation and Development (OECD), the International M ...
The World Bank is an international financial institution that provides loans and grants to the governments of low- and middle-income countries for the purpose of pursuing capital projects. The World Bank is the collective name for the Inter ...
, and other partners, in the context of the Marrakech Action Plan for Statistics.