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  • Lauren Batchelor

Hidden & Transient Population Estimates

What are H&T populations?

The Office for National Statistics regularly releases estimates of the ‘usually resident population’ in local authority districts and small-areas through annual mid-year population estimates and decennial censuses. ‘Usually resident’ refers to the place at which a person has lived continuously or intends to live for at least 12 months, excluding temporary absences for holidays or work.

Whilst these statistics provide an estimate of the usually resident population of an area, there are important sub-populations that are not captured, which can be ‘hidden’ in their nature or have a relatively short-term and ‘transient’ impact upon local populations, referred to as Hidden and Transient (H&T) populations. This includes people with second addresses, tourists, and irregular migrants (i.e. people in the UK without legal residence).

For a range of industries, robust and timely estimates of these H&T populations can be key for resource, infrastructure and service planning.

H&T Population Model

To enable the estimation H&T populations, Edge Analytics has developed its proprietary H&T Population Model, providing estimates for the following sub-populations:

· Irregular Migrants

· Short-Term Residents

· Second Addresses

· Domestic Day Visitors

· Domestic Night Visitors

· Foreign Night Visitors

Using evidence from a mix of Census, survey and administrative sources, plus published academic research, the H&T Population Model provides ‘Low’, ‘Medium’, and ‘High’ H&T population estimates for output areas in England and Wales, which can be aggregated to bespoke geographies.

H&T population estimates are delivered via an MS Excel data deliverable, with an accompanying methodological report.

Data Updates

Following a series of key data releases, the evidence underpinning the H&T Population Model has been recently updated, the first major update since the 2011 Census and onset of the COVID-19 pandemic.

Census evidence provides the most definitive statistics on short-term residents and second addresses in England and Wales, with the 2021 Census providing a valuable update to the number and distribution of short-term residents and second addresses in England and Wales.

Suspended during the COVID-19 pandemic, Visit Britain has recently released its latest survey evidence on domestic day visitors and domestic night visitors in Great Britain, published in the GB Day Visitor Survey and GB Tourism Survey, which resumed in April 2021. Alongside this, Visit Britain has also released the latest evidence from the International Passenger Survey, central to estimates of foreign night visitors.

Evidence from the Department for Work and Pensions’ National Insurance Number Registrations, the Royal Mail’s Postcode Address File, and NOMIS’ Business Counts have also enabled the evidence on the distribution of H&T populations to micro-locations to be refreshed.

Case Studies

In addition to the usually resident population, H&T populations can result in substantial permanent or seasonal uplifts to the population of an area, particularly in areas that are popular tourist destinations or receive large numbers of short-term residents for work or study.

For these areas, the estimation of H&T populations is essential for the planning for local services, such as the provision of utilities and access to health services, and an important consideration for local business planning and decision making.

Edge Analytics’ H&T Population Model is trusted by the water industry, and is used to quantify the additional population contributing to water usage and requiring waste water services. Details on our work with Dwr Cymru Welsh Water can be found in our case study below.

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