Methodology division at the Office for National Statistics

The methodology division at the Office for National Statistics (ONS) helps ensure that Government Statistical Service (GSS) statistics are underpinned by robust statistical methodology and meet accepted quality standards.

The division supports the entire statistical production chain, and provides advice across the GSS.

The mission for the division is: Better Methods, Better Statistics, Better Decisions.

Projects the division has worked on

The census includes everyone doesn’t it? Well, it doesn’t quite achieve that. Every effort was made to ensure everyone was counted in the 2011 Census, however no census is perfect and some people were inevitably missed.

The methodology division developed a statistical methodology which measured this ‘undercount’ of the population and made sure that the statistics published from the census represented everyone. This statistical methodology produced the key population estimates from the 2011 Census which are used as the basis for all population statistics in the ten years following the census.

Find out more about the Census coverage assessment.

New data sources and methods are being introduced into the production of consumer price statistics from 2023. The new data sources, namely web-scraped and scanner, have the potential to improve the quality of UK consumer price statistics through increased coverage and more timely data.

To be able to calculate a price index we must know which category each product in the data belongs to in line with the ONS product hierarchy e.g. women’s dress, men’s shirt. The volume of this new data means we can no longer manually assess each product. Instead we are researching using machine learning to automatically classify products.

Using a mixture of natural language processing (NLP) and classification algorithms (such as XGBoost) we have developed a prototype classification method for clothing data. Once classified the data are able to move through the other stages of calculating a price index. This research will now be broadened to apply these methods to other price datasets such as groceries.

Find out more about the automated classification of web-scraped clothing data in consumer price statistics.

Methodology were involved from the outset of this fast-paced development. As the Government needed timely data of the precise impact of the pandemic on UK businesses, administrative data sources – neither timely nor specific – were not suitable, so a traditional survey, in which ONS excels, was decided upon.

Instead of taking months to develop and design, BICS was in the field collecting data in a matter of days. This was only possible due to questionnaire design experts helping design, test and route questions – this has continued throughout the survey, as questions are added/deleted regularly, and the more data we collect the more we can refine the electronic questionnaire.

The design of the sample, the data cleaning methods, and the estimator used took a little longer – initially the design was business-area led, and resulted in a purposive sample which could only be used to provide information on the businesses that responded, not the whole economy. Innovative imputation methods developed by methodology were implemented quickly to help with the high non-response rates. The methodology redesign of the survey to make it representative of the whole business population, and allow inference from results about the impact on the UK economy not just the sample, took longer to be implemented – although it was developed at the outset.

Latest developments have involved methodology developing measures of precision around estimates, so that standard errors, coefficients of variation and confidence intervals can be published around key variables collected.

Business insights and impact on the UK economy

Business insights and impact on the UK economy – detailed datasets

Business Impact of Coronavirus (COVID-19) Survey: preliminary weighted results

Business impact of COVID-19 survey results

Methodology have been involved throughout this long running project, from questionnaire design and testing to currently providing the methods and support for the transformation to the new processing pipeline. The new DTrades output will bring together short-term output indicators for Retail, Motor Trades and Wholesale industries (standard industrial classification divisions 45, 46 and 47) as part of a large-scale Business Statistics Transformation programme.

Historically, short-term output from these industries have been measured using the Retail Sales Index (RSI) and Monthly Business (MBS) Surveys. These surveys are being transformed such that data will be collected electronically under the newly designed Monthly Turnover Survey, to facilitate the production of the new DTrades output.

As key aspect of this transformation work programme, the DTrades output will incorporate the use of both survey and administrative His Majesty’s Revenue and Customs (HMRC) Value Added Tax (VAT) data. Methodological research has taken place to determine the ‘partition’ between survey and VAT data.

Currently working closely with IT colleagues, we are delivering on five improved methods: Estimation, Selective Editing, Date Adjustment, Winsorization and Imputation. When completed these generic methods will be available through the Statistical Methods Library (SML) for use throughout ONS and wider government areas.

Find out more about DTrades in survey methodology bulletin no. 79.

Specific methods used

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Opportunities to work for us

The division recruits through adverts on Civil Service Jobs and through the Civil Service Fast-Stream scheme.


The division supports the annual Government Statistical Service Methodology Symposium.

Find out information about previous conference agendas and presentations.

Related links

Methodology pages for other National Statistics Institutes:

Australian Bureau of Statistics

CBS Netherlands

Central Bureau of Statistics Israel

Central Statistics Office Ireland

National Institute of Statistics Italy

National Records of Scotland

Northern Ireland Statistics and Research Agency

Statistics Canada

Stats New Zealand

The National Institute of Statistics and Economic Studies France

US Census Bureau