Foreword

Timothy Trainor, former chief geospatial scientist, US Census Bureau; former co-chair, UN Committee of Experts on Global Geospatial Information Management

Having worked on five decennial censuses in the US for a large and diverse population within a varied landscape, I have experienced many challenges, difficulties, successes, and celebrations in census taking. In the US, each decade provided opportunities for change and advancement. The 1980 Census experienced inconsistencies between changed boundaries, an outdated road network, and miscoded addresses. There also were demands for data at lower levels of geography to help local and state governments in their responsibilities. In response, the 1990 Census saw the development of a single database with GIS applications from which all geographic products were derived so that changes could be applied consistently. Changes also included a nationwide geographic framework for small areas. To address calls for a more complete statistical frame, the 2000 Census focused on creating a national address list that helped assure a more complete count. The next logical requirement, knowing and using the location of the addresses, was a major focus of the 2010 Census and was made possible by the growing use of GPS technology. As the 2020 Census nears, the use of satellite imagery to aid in address verification and the correct alignment of roads (and thereby many boundaries) is helping to assure solid geospatial information in support of the census.

A census is a primary source of data for each country. The data collected is usually part of a full census in which every household participates in the count. It is not a sample survey, it is not secondary or tertiary data; rather, it is the raw data that is then tabulated and aggregated to levels that are important to data users, leaders, decision-makers, and, in many cases, the law. The framers of the US Constitution outlined the importance of a census by calling for an enumeration every ten years in Article I, Section 2. Its importance was further acknowledged by assigning responsibility as the director for the first census in 1790 to Thomas Jefferson. For many countries, a census is foundational—it provides data and information on current conditions as well as future opportunities and challenges.

However, the numbers on their own are not relevant without an association to location. This is where geography plays its vital role. It answers the question “where” for a summary of people within a household, their age, their gender, their relationship to each other within the household, their health, economic condition, employment, and whatever other question may be included in a country’s census count. Knowing the “where” of a population’s characteristics offers an important and interesting view on a community’s conditions and trends.

A census provides the data that allows us to begin the determination of a cause-and-effect relationship to important questions posed by “why.” Why so many people in this area and so few in that area? Why are there greater health issues in this area? Why is employment high or low here? Why are schools here and not there where school-age children live? Why is crime more prevalent in this one particular area? Why does this area appear healthy while that area doesn’t? The questions are boundless, and the answers are enlightening. Based on these realizations, more “where” questions can lead to solutions, growth, and planning. Where are new or better transportation facilities in demand? Where is a new hospital or health-care unit required? Where are the best building locations for new schools or refurbishing of existing schools?

The data collected during a census, when combined with location, starts the journey of a transformation to valuable information. The statistics about the nation, its regions, its subnational governments and possibly even its communities and neighborhoods open the door to expanding knowledge of its inhabitants. That often leads to a better understanding of the conditions and opportunities in each of these areas. New development, improvements to services, correction to problems, innovation, and improved economic prospects are examples of potential outcomes resulting from the availability of complete and accurate census statistical data.

Geospatial information is needed for each phase of the census—collecting the data, tabulating the counted household numbers, disseminating aggregated tabulations, and analyzing the results of the census. National Statistical Offices (NSOs) may have a small cadre of geographers to support statistical work. Conducting a census requires geospatial information normally maintained by a National Mapping Agency (NMA) or National Geospatial Agency (NGA). For this reason alone, a national census is a collaborative effort. It is best for NSOs and NMAs or NGAs to work together on this common national goal.

The United Nations is leading efforts on the importance of data. In 2011, it formed a Committee of Experts on Global Geospatial Information Management (UN-GGIM). NGAs and NSOs actively work together on important topics to advance their mandate (http://ggim.un.org/). Since its inception, much good work has been done that helps nations plan and conduct their national census. Topics like global fundamental geospatial data themes, the integration of statistical and geospatial information, geodetic reference frames that contribute to data quality, and geospatial information supporting the Sustainable Development Goals, for which significant amounts of census data are required, are examples of work underway.

To ensure that each household is included in the census, the country usually is divided into some type of enumeration area (EA) or enumeration district (ED). No area is left out of this delineation. Enumerators are then assigned to one or more EAs and they conduct the count. Enumerators must know where the EA is and what its boundaries are so that they neither undercount nor overcount within their assignment area. A census map that shows the details of an EA is needed to ensure that assignments are known and clear. This minimally includes the EA boundary, roads, paths, and observable features like rivers as well as geographic names for orientation.

Today, technology has simplified past practices in census taking. A phone or tablet enabled with GPS can assist enumerators in knowing where they are relative to their assignment area, which is depicted on a map on their mobile device. Systematically walking to each household, recording its location, and recording answers to the census questionnaire links the important raw data offered by the respondent to a geographic location. The confidentiality of each household’s response is paramount in gaining support from respondents for their participation in a census. Security of the data takes on new forms with each technological development.

The confidentiality of responses is assured through various statistical techniques and checks. A household’s response with its location is used in adding that response to others within the EA, thereby aggregating the results to a larger geographic area. Using the geographic code of the response (geocode) makes this possible. This allows us to aggregate the data together with other responses within predefined geographic areas that are deemed important for various uses of census data—for example, the combined numbers for the EA or a village or city. This begins the tabulation phase of a census.

It is crucial that data disseminated from a census offer complete and accurate results. While important, having results only at a national level is extremely limiting to the value of a census. The more data that is available and the smaller the level of geography in which data is made available multiplies the positive benefits to the residents of a nation and its communities.

In 2015, the UN Sustainable Development Agenda was agreed to by nations of the world. With 17 goals, 169 targets, and over 230 indicators, the need for small-area data is now paramount if we are to realize the vision of leaving no one behind. The availability of statistical data from the census aligns with determining the appropriate level of geography to meet not only the basic indicator framework but also, ultimately, the intersection of targets and indicators for more complex relationships.

The notion of counting people seems fairly simple. While the basic task of enumerating the population is manageable, many factors complicate this important government function. Counting everyone, regardless of how difficult or how remote; completing census operations and tabulating results in a short time frame; assuring the security of enumerators and the census process; hiring and assigning sufficient numbers of census takers and supervisors; counting everyone once, only once, and in the right location; applying tested cost-effective technologies; evaluating coverage and accuracy of the census; assigning the results to the correct meaningful geography; and widely disseminating results in a timely way are but a few of the challenges in planning and implementing a national census.

Not many books tell you how to conduct a census. In fact, no single book can serve as a recipe for conducting the census. Each country differs in its circumstances. Mandates to carry out censuses vary. The readiness and preparations needed for embarking on a census differ. Even with these diverse variables, important references such as GIS and the 2020 Census: Modernizing Official Statistics offer guidance and help in this critically important government responsibility. Sources like this book help countries account for basic functions and address evolving technologies that can simplify and improve the inordinate scope of conducting a census.

A census is, without question, the largest civilian activity for a nation, larger than a national election or any similar activity. Because it is household based, knowing the geographical location of each household is important to ensure that everyone is included. It consists of many linked operations that span multiple activities for planning, for conducting the census, for processing the numbers, and for disseminating the results. Each activity offers opportunities for problems and challenges. The effective use of GIS technology minimizes risks associated with traditional manual approaches that oftentimes are related to those problems and challenges. As census workers encounter questions or seek solutions to a problem, or look to technology to solve a challenge, reaching for GIS and the 2020 Census: Modernizing Official Statistics is a good first step toward realizing a positive outcome.