A traditional census is conducted at regular intervals and generally involves distributing a survey to every household, either by mail or electronically, or through in-person visits by enumerators. These forms typically include demographic questions about how the individuals are residing. According to the United Nations Economic Commission for Europe, this method has several drawbacks. It is a costly operation due to the large number of people involved, poses challenges in enumerating some subgroups -“particularly those characterized by high mobility,”- and is usually carried out once every ten years, meaning the data can quickly become outdated.

The register-based census, rather than collecting information directly from each household, relies on existing administrative records—such as social security data, tax filings, and education records—to compile detailed population profiles. As a result, residents are not required to fill out any survey forms, since the necessary data is already held by various government agencies. The use of administrative registers offers opportunities for cost reduction and more frequent information production, which can contribute to monitoring goals; however, countries might lack the legal foundation to use personal data and/or the capacity to preserve the registers (United Nations Statistics Division, 2021). The United Nations published a Handbook about this method.

The rolling census captures a country’s demographic data continuously; it was first implemented in France. In this approach, random samples of addresses within each administrative area are selected and surveyed similarly to a conventional census. Census workers then proceed to new randomly selected addresses, repeating the process until the full population has been covered. Most locations are surveyed more than once during the cycle. The entire population is counted over a seven-year span, with a new cycle beginning as soon as the previous one concludes. 

The different approaches can be combined to leverage the method and obtain more accurate results.

Given the Population Census infrequency and sized samples, this method does not “provide actionable data for policy makers” (OECD, 2025).  Timeless is also a challenge. Depending on the geographical scale and analytic systems, processing census data can take time and results usually become available approximately one year after the Census Day.

The information collected through a census is best used in establishing historical tendencies on population, housing, and socioeconomic conditions. If gathered, data analysts should review and disseminate information on the total number of people experiencing different forms of homelessness, including demographic characteristics, housing and services provided, and other relevant trends and information.

The results of a census can serve a wide range of purposes across government, civil society, and community sectors. It guides decision-making and budget planning at all levels of government, including public services such as transportation, healthcare, housing, education, and emergency response, as well as for targeting resources to vulnerable populations (Government of Daytona). In Mexico, the census data integrates homelessness enumeration, and it is also utilized to inform public policies and identify subgroups with particular needs regarding housing, education, health, etc.

Stakeholders should use the published reports to raise awareness of homelessness and as a foundational tool for shaping policies and understanding demographic and economic trends nationwide.

The use of traditional census data to measure homelessness has significant limitations. Most local governments conduct censuses infrequently and without methodologies tailored to identify people experiencing homelessness, leading to consistent undercounts—particularly among socially marginalized or hard-to-reach groups who fall outside standard outreach efforts. Since homelessness is not directly measured, analysts must rely on indirect indicators and assumptions to estimate prevalence, which introduces uncertainty.

While the census in countries like Australia offers comprehensive coverage, its ten-year cycle is more useful for identifying long-term trends than for capturing accurate, real-time data on homelessness.

The 2018 New Zealand Census, which employed a Point-in-Time methodology to enumerate homelessness, acknowledged limitations and challenges in data collection, particularly due to lower-than-expected participation rates, which affected the reliability and completeness of the data. This was especially concerning for Māori and Pacific populations, who were likely underrepresented, leading to an undercount of those experiencing “severe housing deprivation.”

These gaps highlight a critical weakness in relying solely on census data to understand housing needs and underscore the need for alternative data sources to more accurately and consistently monitor homelessness and housing insecurities.