National statistics

Benefit in kind statistics Background Quality Report

Published 29 September 2022

1. Contact

• Organisation unit - Knowledge, Analysis and Intelligence (KAI)
• Name – L Matlak
• Function - Statistician, Personal Taxes
• Email – personaltax.statistics@hmrc.gov.uk

2. Statistical presentation

2.1 Data description

This publication provides statistics about the company cars provided as benefits in kind to employees by employers. These tables show the number of recipients of such benefits, the taxable value of the benefits and the Income Tax and National Insurance contributions (NIC) liabilities on them. Breakdowns are provided by income level and geographical region of the recipient and by the Carbon Dioxide (CO₂) emission level and fuel type of the vehicle.

Additionally, this publication also includes statistics on the total taxable value of Class 1A taxable benefits in kind.

2.2 Classification system

The number of company car benefit recipients is broken down by CO₂ emission band and fuel type.

2.3 Sector coverage

Employers operating in all industries can provide benefits in kind to their employees.

2.4 Statistical concepts and definitions

Company cars

A car for which an employee is chargeable to car benefit.

Company car benefit

If an employer makes a car available to an employee for personal use they are liable to the car benefit charge, also known as company car tax. See booklet 480, for more information.

Car benefit recipient

A reported recipient of company car benefit.

Fuel benefit recipient

A reported recipient of company car fuel benefit.

Car benefit taxable value

Taxable value of reported company car based on the car’s list price (with accessories) and appropriate percentage (linked to the car’s CO₂ emissions).

Car fuel benefit taxable value

Taxable value of reported car fuel benefit calculated using the car fuel benefit multiplier and the appropriate percentage used to calculate the car benefit (linked to the car’s CO₂ emissions).

Car benefit Income Tax liability

The Income Tax in respect of car benefits in kind for an individual is calculated as the difference between liabilities arising with and without the value of benefits included.

Car fuel benefit Income Tax liability

The tax in respect of car fuel benefits in kind for an individual is calculated as the difference between liabilities arising with and without the value of benefits included.

Car benefit NIC liability

The NIC liability in respect of car benefits in kind for an individual are calculated as the difference between liabilities arising with and without the value of benefits included. Employers are required to pay Class 1A NICs, there is no NIC liability on employees for car benefit

Car fuel benefit NIC liability

The NIC liability in respect of car fuel benefits in kind for an individual are calculated as the difference between liabilities arising with and without the value of benefits included. Employers are required to pay Class 1A NICs, there is no NIC liability on employees for car fuel benefit

CO₂ emissions

Reported CO₂ emission of company cars. The way that a vehicle’s CO₂ emissions are measured changed between 2018 and 2020. The older test procedure (the NEDC or ‘New European Driving Cycle’ test procedure) was replaced with a new test procedure called the Worldwide Harmonised Light Vehicle Test Procedure (WLTP). From September 2018 all new cars were tested using the WLTP, though before April 2020 the CO₂ emissions measured with this test were converted back to equivalent NEDC figures for tax calculations. All new cars will use the WLTP CO₂ measurement for tax calculations from April 2020.

Vehicle fuel type

Reported fuel type of company cars, diesel or petrol.

The company car benefit charge depends on the list price of a car, on its fuel type and on its reported CO₂ emissions figure. There is a “diesel supplement” which increases the car benefit charge of diesel-powered cars compared to otherwise equivalent vehicles.

Before April 2011, the diesel supplement did not apply to diesel cars that met the Euro IV emissions standard and were first registered before January 2006. From April 2018, the diesel supplement does not apply to diesel cars that meet the Real Driving Emissions 2 (RDE2) standard.

Diesel cars meeting either the Euro IV emissions standard or the RDE2 standard are classified as diesel in these statistics, even if not liable to the diesel supplement. The non-diesel category of fuel includes petrol, conversion, hybrid, bio-fuel and bio-ethanol cars.

Total income

Total income inclusive of the benefit amount comprises all incomes assessable for Income Tax. This includes total earned income as well as total investment income; not just earnings from employment. Total earned income includes state benefits as well as earnings from employment such as taxable incapacity benefit, other taxable social security benefits and jobseeker’s allowance payments. Gross profits assessable for all sources of self-employment income, taxable pay on termination of employment, and pensions are also included. Total investment income would include net income from UK and overseas property, net interest from UK banks, building societies and other deposit takers, dividends from shares in UK companies and unit trusts, gains on life policies with tax treated as paid, gross interest paid, and any other interest and dividends from UK and overseas savings and investments charged at 20%.

Class 1A taxable benefits in kind

Taxable value of Class 1A taxable benefits in kind. Class 1A National Insurance contributions are payable to most benefits provided to employees. They are also payable on non-contractual termination payments that exceed the £30,000 threshold; and non-contractual and non-customary testimonial payments paid to a sportsperson by a sporting testimonial committee which exceeds the £100,000 threshold.

Further details on the calculation of taxable values for company cars, car fuel benefit, and other benefits in kind can be found in HMRC Tax Guide (Expenses and Benefits).

In general, the taxable value of benefits in kind may be reduced by contributions paid by the employee for the benefit in kind. The final value of the benefit for tax purposes will be used to assess the Class 1A NICs that the employer (or third party) is liable to pay. Taxable benefits not already subject to Class 1 NICs are liable for Class 1A NICs unless they are exempt. Further details about the taxation and NICs treatment of benefits in kind and expense payments can be found on the HMRC and gov.uk websites using the following links:

• Employment Income Manual

• Expenses and Benefits: A tax guide (Booklet 480)

• Class 1A National Insurance contributions on benefits in kind: A guide for employers (Booklet CWG5)

• Expenses and benefits for employers

2.5 Statistical unit

The unit in the statistics is an individual who is a recipient of a benefit in kind. For Table 2E average CO₂ emissions the unit is a company car benefit.

2.6 Statistical population

All individuals in receipt of company car or car fuel benefit in kind (Tables 1-4) or Class 1A benefit in kind (Table 5), in the UK.

2.7 Reference area

The geographic region covered by the data is the United Kingdom (UK).

2.8 Time coverage

The statistics cover the time period from tax year 2011 to 2012 until the latest tax year for which information on benefits in kind is available.

3. Statistical processing

3.1 Source data

The published estimates in Tables 1-4 are based on the data collected from P11D forms, RTI submissions and the Survey of Personal Incomes (SPI). The figures in Table 5 for total amount of Class 1A National Insurance paid on all benefits in kind (including company cars), and the corresponding value of those benefits are calculated from receipts data in HMRC’s Enterprise Tax Management Platform (ETMP) system.

P11D forms

At the end of each tax year, employers must provide HMRC with details of taxable expenses and employment benefits provided to directors and certain employees. Employers are required to complete a separate P11D form for each employee whose expenses and benefits they report. P11D data are captured on the HMRC Employer Compliance System (ECS).

RTI submissions

From April 2016 the requirement to report certain benefits in kind on the P11D form has been removed for those employers who register to deduct the tax due on those benefits in kind directly from payroll. From April 2017, employers who payroll company cars or car fuel benefits could voluntarily report details as part of their regular PAYE returns on RTI (Real Time Information). From April 2018, reporting these details on RTI is a requirement for employers who payroll company cars or car fuel benefits. Other benefits in kind are reported as a total figures per individual so of limited analytical value.

Survey of Personal Incomes

The Survey of Personal Incomes (SPI) is a sample survey derived from data held by HMRC on persons who have been in contact with HMRC over the tax year through the PAYE, SA or repayment claims processes. The survey consists of a systematic random sample of individuals each tax year. For each individual in the sample, SPI includes information on incomes assessable to income tax for the year, together with some basic information on individual characteristics, for example age and gender.

The SPI sample size has increased over time to around 700,000. It is made up of three separate samples drawn from three different HMRC administrative systems. SPI datasets are available for public use via the UK Data Archive at Essex University (registration required).

SPI is matched against the ECS and RTI data to enable tax liability and income calculations.

Enterprise Tax Management Platform (ETMP)

The value of benefits is calculated from receipts data in HMRC’s Enterprise Tax Management Platform (ETMP) system. ETMP is used across HMRC to manage an increasing number of HMRC’s taxes and duties.

3.2 Frequency of data collection

Employers provide HMRC with a P11D return for the relevant tax year on an annual basis.

RTI and ETMP data is received by HMRC on a daily basis.

3.3 Data collection

P11D forms are submitted by employers and captured on the HMRC Employer Compliance System (ECS) at the end of each tax year. RTI returns are submitted to HMRC by employers when they run their payroll.

3.4 Data validation

Checks carried out on the data include:

• Automated checks take place when loading data into the analysis database. Inconsistencies are automatically ‘repaired’ by imputing missing values, removing duplicates and resolving data issues where possible; a small number of records are removed.

• Analysts check that the number of records loaded into the analysis database is as expected.

3.5 Data compilation

Following the end of each tax year an individual level dataset, containing all benefits in kind and taxable expenses that have been reported on a P11D return, is compiled.

For tax years after April 2017, the P11D data is supplemented with RTI data to account for car and car fuel benefits that were reported on payrolling.

The number of recipients and the amount of each car and car fuel benefit can be obtained from the combined P11D and RTI data, and are reported in Tables 1, 2, 3 and 4.

A data cleaning exercise is performed to make sure the source data are fit for purpose. Some company cars were reported on both P11Ds and in RTI data. For these cases, an exercise is carried out to identify the duplicated company cars and remove one version.

Information from the Survey of Personal Incomes (SPI) is then merged onto the combined P11D and RTI data to obtain information relating to total income and tax liability as this is not currently held on the combined data. Not all individuals in the combined P11D and RTI data are included in the SPI sample, so the merged dataset is only a subset of the benefits in kind population.

Table 5 reports the total amount of Class 1A National Insurance contributions paid on all benefits in kind (including company cars), and the corresponding value of those benefits. These figures are calculated from receipts data in HMRC’s Enterprise Tax Management Platform system (ETMP). The figures do not include any termination payments or sporting testimonial income, some of which are subject to Class 1A NIC.

Calculating Income Tax and National Insurance Contributions

Tax and NIC liabilities in respect of benefits in kind for an individual are estimated as the difference between liabilities arising with and without the value of benefits included as income. These can be estimated for individuals in the SPI sample in receipt of benefits in kind data using the information SPI provides on marginal rates of tax faced by Income Tax payers. The calculations take account of headline tax rates and also various deductions which reduce an individual’s tax liability such as the personal allowance and tax reliefs.

The difference between the tax liabilities including and excluding benefits is summed over all merged cases (and grossed to the UK population) and then divided by the grossed benefits in kind total to give an average (marginal) tax rate per pound of benefit. This average tax rate (for each benefit) is then applied to the total taxable value derived from the combined P11D and RTI data to obtain an overall tax liability estimate for all in receipt of benefits in kind in scope of this publication.

This approach effectively considers the benefit in kind as the final marginal element of income, and consequently the tax liability reflects the taxpayer’s highest effective rate of tax. An alternative approach would have been to attribute the amount of tax to the benefits in kind based on the proportion of the benefits in kind value in total income. This would have resulted in lower average tax rates compared to the approach adopted with a considerable impact on tax liabilities calculated.

The methodology adopted should be better suited to most users’ needs. The tax liability shown represents the tax figure which would be affected by any changes to rules for determining taxable value of benefits, or by any change to take-up of benefits in kind.

A corresponding methodology was adopted for the NIC liability.

Table 1 reports the number of recipients and the amount of car and car fuel benefits along with their estimated tax and National Insurance contributions.

Estimating breakdown of totals according to total income

Table 3 provides breakdowns of total values according to range of total income for taxpayers in receipt of benefits.

Estimates for each range are found from the merged data, as the combined P11D and RTI data do not contain all details of income. The estimates are grossed up using standard SPI grossing factors, but a further adjustment factor is then applied in order that the total taxable benefit value for all cases is equal to the total figure known from the full data. The same adjustment factor is used for both benefit value and number of recipients, with the result that the number of recipients reported by income band will not sum exactly to the total number of recipients from the full data.

It is not possible to adjust the number of recipients to the value in the full data by a different factor than that used for the amount of benefit without distorting estimates of average benefit value.

Calculation of number of car recipients split by CO₂ emission

Table 2 reports all car benefits split by CO₂ emission and by fuel type. However, since a recipient can have more than one car benefit in the tax year, it was necessary to apportion that recipient between their multiple car benefits, so that they would not be counted more than once. A recipient was therefore apportioned between their car benefits according to the length of time they had each benefit.

Where a recipient only had a car benefit for part of the year, the car benefit, tax and NIC values in the table reflect the part year. However the individual still counts as one person for the purposes of the recipients column. Where a recipient had multiple car benefits at the same time so that they had the equivalent of one benefit for greater than a year, this was scaled down to a year, and the recipient apportioned between them.

Imputation of CO₂ values and fuel type

CO₂ values are reported on the P11D and RTI data where an employer reports a car benefit. Sometimes these are missing or are implausible values. Where other supporting data can help impute the missing or implausible value, this has been done prior to producing the figures in Table 2. Typically fewer than 2% of car benefit values are imputed for any given year.

Table 2 also includes some information on average CO₂ emissions (including a breakdown by fuel type).

Projections to next tax year

The latest available SPI data are projected forward one year to help produce the provisional tax liability estimates that appear in Table 1.

The number of recipients and taxable value of the benefit are obtained from P11D and RTI data and are not based on projections. The projected SPI is then merged onto the early extract of P11D and RTI data for that year to obtain information relating to total income and tax liability. The average tax rate per pound is then calculated in the same way as previously described. This average tax rate and the Class 1A NIC rate are then applied to the combined P11D and RTI data to produce provisional estimates.

4. Quality Management

4.1 Quality assurance

All official statistics produced by HMRC statisticians, must meet the standards in the Code of Practice for Statistics produced by the UK Statistics Authority and all analysts adhere to best practice as set out in the ‘Quality’ pillar.

Analytical Quality Assurance describes the arrangements and procedures put in place to ensure analytical outputs are error free and fit-for-purpose. It is an essential part of KAI’s way of working as the complexity of our work and the speed at which we are asked to provide advice means there is a high risk of error which can have serious consequences on KAI’s and HMRC’s reputation, decisions, and in turn on peoples’ lives.

Every piece of analysis is unique, and as a result there is no single quality assurance (QA) checklist that contains all the QA tasks needed for every project. Nonetheless, analysts in KAI use a checklist that summarises the key QA tasks, and is used as a starting point for teams when they are considering what QA actions to undertake.

Teams amend and adapt it as they see fit, to take account of the level of risk associated with their analysis and the different QA tasks that are relevant to the work.

At the start of a project, during the planning stage, analysts and managers make a risk-based decision on what level of QA is required.

Analysts and managers construct a plan for all the QA tasks that will need to be completed, along with documentation on how each of those tasks are to be carried out, and turn this list into a QA checklist specific to the project.

Analysts carry out the QA tasks, update the checklist, and pass onto the Senior Responsible Officer for review and eventual sign off.

4.2 Quality assessment

The QA for this project adhered to the framework described in ‘4.1 Quality assurance’ and the specific procedures undertaken were as follows:

Stage 1 – Specifying the question

Up to date documentation was agreed with stakeholders setting out outputs needed and by when; how the outputs will be used; and all the parameters required for the analysis.

Stage 2 – Developing the methodology

Methodology was agreed and developed in collaboration with stakeholders and others with relevant expertise, ensuring it was fit for purpose and would deliver the required outputs.

Stage 3 – Building and populating a model/piece of code

• Analysis was produced using the most appropriate software and in line with good practice guidance.

• Data inputs were checked to ensure they were fit-for-purpose by reviewing available documentation and, where possible, through direct contact with data suppliers.

• QA of the input data was carried out.

• The analysis was audited by someone other than the lead analyst – checking code and methodology.

Stage 4 – Running and testing the model/code

• Results were compared with those produced in previous years and differences understood and determined to be genuine.

• Results were compared with comparable independent estimates, and differences understood.

• Results were determined to be explainable and in line with expectations.

Stage 5 – Drafting the final output

• Checks were completed to ensure internal consistency (e.g. totals equal the sum of the components).

• The final outputs were independently proof read and checked.

5. Relevance

5.1 User needs

This analysis is likely to be of interest to users under the following broad headings:

• national government – policy makers and MPs

• regional and local governments

• academia and research bodies

• media

• fleet owners, manufacturers and company car drivers

• general public

5.2 User satisfaction

Users can provide feedback by contacting the relevant statistician whose details are provided in the publication.

In addition, a user engagement exercise was carried out between 30 September 2020 and 31 December 2020 to better understand how the new statistics can meet user needs. Benefits in kind statistics: user engagement exercise 2020.

5.3 Completeness

Some company cars are not included in the source data used to produce the statistics and are therefore excluded from the tables 1-4. They are:

Unreported or uncaptured payrolled company cars

These are company cars where the employer has deducted tax through their payroll system. Before April 2016 a small number of cars were subject to ‘informal payrolling’. In such cases P11Ds were submitted to HMRC but not captured on ECS.

From April 2016, employers have been able to register for ‘voluntary payrolling’, removing any requirement to submit a P11D return when deducting tax through the payroll system. The number of schemes payrolling company cars has increased year on year since April 2016.

This has created incompleteness in HMRC’s data in the following ways:

• in the first year of voluntary payrolling (tax year 2016 to 2017), there was no system for reporting payrolled company cars

• in tax year 2017 to 2018, payrolled company cars could be reported in PAYE submissions via Real-Time Information (RTI) on a voluntary basis

• in tax year 2018 to 2019 reporting of payrolled company cars became mandatory but analysis suggests there is significant under-reporting

Company cars on late arriving P11D forms

P11D forms are due to be filed in the July following the end of the tax year. The data used in the published tables come from extracts from live data and any P11D forms processed after the extract dates will not be reported in the tables. These P11Ds will either be new cases or changes to existing cases. Analysis suggests that the additional proportion of benefit value likely to arrive after the extract date is less than 0.1% for tax year 2019 to 2020, and less than 0.5% for earlier years.

6. Accuracy and reliability

6.1 Overall accuracy

This analysis is based on administrative data, and accuracy is addressed by eliminating non-sampling errors as much as possible through adherence to the quality assurance framework.

The potential sources of error include:

• employers providing incorrect information to HMRC

• sampling errors for those figures that depend on the Survey of Personal Incomes

• mistakes in the code used to produce the statistics

• errors, for example transposing figures, when producing the data tables and commentary to be published

6.2 Sampling error

There will be sampling errors for those figures which depend on the Survey of Personal Incomes (tax and NIC liability estimates, and breakdowns by total income). However the sample size is large and so the estimates should be robust.

6.3 Non-sampling error

Coverage error

See section 5.3 for information on issues with completeness in HMRC’s data which has a bearing on the coverage of these estimates.

Measurement error

The main source of measurement error is from employer errors and omissions in their submissions to HMRC.

Nonresponse error

Non-response error is not applicable to these statistics as they are not based on a survey.

Processing error

It is possible that errors exist in the programming code used to analyse the data and produce the statistics. This risk is reduced through developing a good understanding of the complexities of benefits in kind, and thoroughly reviewing and testing the programs that are used.

6.4 Data revision

Data revision – policy

The United Kingdom Statistics Authority (UKSA) Code of Practice for Official Statistics requires all producers of Official Statistics to publish transparent guidance on the policy for revisions.

Data revision – practice

This analysis is published annually and includes an estimate of liabilities for the latest tax year for which P11D data is available, along with updated estimates for the previous year taking account of late-filed and amended P11D returns. Revisions for the previous tax year are small, less than 1% mainly due to the SPI survey update but reflect the latest position for employees and any new data received since the previous publication.

6.5 Seasonal adjustment

Seasonal adjustment is not applicable for this analysis.

7. Timeliness and punctuality

7.1 Timeliness

Due to the time needed to receive and process tax returns and information provided by employers, the first publication of data for a new tax year normally occurs 15 months after the end of the tax year, in the form of projections in Table 1.

The SPI data for the new tax year (used to calculate tax and NIC liabilities and breakdowns by income) does not become available until several months later, and the P11D data are also subject to revision. Consequently full and final statistics are published in the following year’s release, 2 years and 3 months after the end of the tax year.

7.2 Punctuality

In accordance with the Code of Practice for official statistics, the exact date of publication will be given not less than one calendar month before publication on both the Schedule of updates for HMRC’s statistics and the Research and statistics calendar of GOV.UK.

Any delays to the publication date will be announced on the HMRC National Statistics website.

The full publication calendar can be found on both the Schedule of updates for HMRC’s statistics and the Research and statistics calendar of GOV.UK.

The punctuality record in recent years has been as follows:

• 2016: published on schedule in June 2016

• 2017: published on schedule in June 2017, revised in February 2018 to correct an error on Class 1A benefits in Table 4.1 and 4.5

• 2018: published on schedule in June 2018, revised in July 2018 to correct an error in the provisional tax liability 2016 to 2017 estimates that appeared in Table 4.5

• 2019: published on schedule in June 2019

• 2020: published in September 2020, three months late, as a result of demand on resources related to the COVID-19 pandemic.

• 2021: published in July 2021, one month late, to allow sufficient time for the preparation and quality assurance of the statistics

8. Coherence and comparability

8.1 Comparability over time

Since these statistics are based on P11D returns, the increasing take-up of voluntary payrolling of benefits in kind has implications for the coverage and completeness of the statistics, and the comparability over time.

Until tax year 2016 to 2017, employers were required to provide HMRC with details of all taxable benefits in kind provided to directors and employees. This information was reported on form P11D at the end of each tax year. From 2016 to 2017, the requirement to make P11D returns has been removed if the employer has registered for voluntary payrolling. Data returned by employers on the P11D return are captured on the HMRC Employer Compliance System (ECS).

Most benefits in kind which are subject to voluntary payrolling do not have to be reported to HMRC. However there is a requirement to report company cars as part of PAYE submissions via Real-Time Information (RTI).

For tax years after April 2017 the P11D data has been supplemented with RTI data. However reporting of payrolled company cars was on a voluntary basis in 2017 to 2018 and analysis suggests there was significant underreporting even after reporting became compulsory in April 2018. Figures for tax year 2016 to 2017 do not include any estimate of the impact of voluntary payrolling, which was introduced from April 2016. Figures for subsequent years are experimental and include voluntarily payrolled company cars which were reported to HMRC. However analysis suggests that significant numbers were not reported even after reporting became mandatory.

Between tax year 2010 to 2011 and tax year 2015 to 2016 the reported number of recipients of company car benefit remained relatively stable. More recently the number of reported company car users has fallen. However the reporting issues noted above mean that there is likely to be a substantial number of individuals in recent years who received company car benefit that (while taxed at payroll) was not properly reported to HMRC.

8.2 Coherence – cross domain

The figures presented on Class 1A benefits in kind have been compared with an alternative source: the amount of Class 1A NIC liability reported to HMRC by employers on the P11Db (summary) form. Differences between the two sources have been investigated and can be attributed to errors in the P11Db source. There are no alternative sources for the information on company cars presented in the tables.

8.3 Coherence – internal

Rounding of numbers may cause some minor internal coherence issues as the figures within a table may not sum to the total displayed. Effort has been made to ensure totals between tables remain constant where appropriate.

9. Accessibility and clarity

9.1 News release

There haven’t been any press releases linked to this data over the past year.

9.2 Publication

The tables and associated commentary are published on the Taxable benefits in kind and expenses payment statistics.

Tables are published in the OpenDocument format, and the associated commentary in an HTML format.

Both documents comply with the accessibility regulations set out in the Public Sector Bodies (Websites and Mobile Applications) (No. 2) Accessibility Regulations 2018.

Further information can be found in HMRC’s accessible documents policy.

9.3 Online databases

This analysis is not used in any online databases.

9.4 Micro-data access

Access to this data is not possible in micro-data form, due to HMRC’s responsibilities around maintaining confidentiality of taxpayer information.

9.5 Other

There aren’t any other dissemination formats available for this analysis.

9.6 Documentation on methodology

The methodology is explained in full in this document.

9.7 Quality documentation

All official statistics produced by KAI, must meet the standards Code of Practice for Statistics produced by the UK Statistics Authority and all analysts adhere to best practice as set out in the ‘Quality’ pillar. Information about quality procedures for this analysis can be found in section 4 of this document.

10. Cost and burden

Because all necessary data for the Benefits in Kind Statistics is obtained from administrative data sources there is no additional burden on employers or HMRC tax inspectors to provide information.

It is estimated to take about 6-8 weeks FTE to produce the annual analysis and publication.

11. Confidentiality

11.1 Confidentiality – policy

HMRC has a legal duty to maintain the confidentiality of taxpayer information.

Section 18(1) of the Commissioners for Revenue and Customs Act 2005 (CRCA) sets out our duty of confidentiality. This analysis complies with this requirement.

11.2 Confidentiality – data treatment

The statistics in these tables are presented at an aggregate level so identification of individuals is minimised, but potentially still possible.

Disclosure in this analysis is avoided by applying rules that prevent categories of data containing:

• small numbers of contributors, and

• small numbers of contributors that are very dominant

If a cell within a table is determined to be disclosive, its contents are suppressed by combining categories.