DASA ROUNDING POLICY
STATUS:
AUTHOR:
OWNER:
FINAL
HOB DASA(WDS)
DASA EXECUTIVE COMMITTEE
ISSUE DATE:
7th May 2009
REVISED:
21st July 2010
Why do we need a policy?
1. Rounding is desirable both as a means of disclosure control and to improve the
clarity of outputs and convey appropriate levels of precision to users. Rounding
needs to be implemented across DASA in a coherent and consistent way.
Reasons for rounding
2. Rounding is DASA’s preferred method of disclosure control in published
statistics. Rounding of small numbers preserves anonymity of data subjects in
aggregate tables. See the DASA policy on Disclosure and Confidentiality for
more details.
3. Rounding can also improve the clarity of tabulated data. In most cases, the extra
detail provided by unrounded figures is not needed, and may obscure the main
features of the data.
4. Rounding figures makes them less precise, but not less accurate. Less precision
can be an advantage, as unrounded figures may mislead users as the accuracy
of the figures. Minor corrections to the underlying data are more likely to affect
unrounded figures than rounded ones.
Excel Formula
5. The Excel 2003 formula for rounding to the nearest 5 is
=IF(AND(A1<>0,ABS(A1)<5),"~",MROUND(A1,SIGN(A1)*5))
6. The Excel 2003 formula for rounding to the nearest 10 with numbers ending in 5
being rounded to the nearest multiple of 20 is
=IF(MOD(ABS(A1),10)=5,MROUND(A1,SIGN(A1)*20),MROUND(A1,SIGN(A1)*10))
What is DASA’s policy?
7. The appropriate rounding scheme will depend on the type of statistics. Rounding
policies for DASA’s main data types are set out below.
8. The rounding policies have been agreed following discussion with subject matter
experts, and taking into account disclosure, precision, specific business
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requirements and practical implementation issues. The different rounding
schemes for different data types reflect the fact that these issues are different for
each data type. If further information is required on the reasons behind the
different policies, you should contact HOB DASA WDS for details.
Manpower Statistics
9. Manpower statistics are considered to be statistics relating to service or civilian
personnel that are not specifically health related.
10. Manpower statistics should normally be rounded to the nearest 10, with numbers
ending in ‘5’ being rounded to the nearest multiple of 20 to prevent systematic
bias.
11. In cases where outputs involve small numbers, figures can be rounded to 5 at the
discretion of the Head of Branch. However care should be taken that such data
are consistent with previously published figures.
12. Data that are considered non-sensitive and are already in the public domain
(including data on rank and sex for senior officers such as published in TSP 9
may be published unrounded in DASA outputs.
13. If a customer (whether internal or external) has a genuine need for unrounded
figures for statistical, research or legal purposes only, then it may be possible to
provide unrounded figures providing the customer signs a written agreement that
states what the data may be used for, and committing not to pass on the
unrounded figures to anyone else. All such cases should be discussed with Head
of DASA PSA. Suggested wording for such an agreement is provided at Annex
A.
14. Unrounded figures should not be provided (even to internal customers) except in
situations covered by 12 and 13 above.
15. Forecast data should also be rounded where possible.
Health Statistics
16. Health statistics are considered to be medical and casualty statistics, and also
statistics on war pensions, the Armed Forces Compensation Scheme, and on
health and safety.
17. Medical information and operational casualty figures should normally be
published unrounded, as exact numbers are often required for research
purposes. However, to prevent disclosure any numbers less than 5 should be
shown as ‘~’. For cases where there is only 1 cell in a row or column that is less
than 5, the next smallest number should also be suppressed so that numbers
cannot simply be derived from totals.
18. Non-medical information such as war pensions, AFCS and Health and Safety
statistics should be rounded to the nearest 5.
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19. There is a risk associated with this rounding policy in that the possibility of being
able to derive numbers less than 5 by comparing different outputs, and thus
potentially being able to derive information about individuals, cannot be ruled out.
However it is considered that the risk of this happening is sufficiently small to be
acceptable.
Financial Statistics
20. Financial statistics encompass a range of information such as defence
expenditure, contracts statistics, trade statistics, and industry and employment
statistics.
21. There are a number of areas of the Department that publish financial data, and in
most cases DASA is not the data owner. For many types of financial data, panMOD disclosure policies are already in place or are being set up.
22. Financial statistics published by DASA should be rounded according to MOD
policy and best practice. More detail on this can be found at Annex B.
Equipment Statistics
23. There are no disclosure issues under the Data Protection Act for equipment data,
so the issue of rounding largely comes down to deciding the appropriate level of
precision for the figures – taking account of data quality and security implications.
24. Equipment statistics should normally be rounded to 10, but may be left
unrounded or rounded to 5 when dealing with small numbers if there is a
requirement for more precise figures. Statistics may also be rounded to 100 or
1000 when dealing with consistently large numbers. Where figures are published
on a regular basis a consistent rounding policy, which may be to leave them
unrounded, should be agreed at the outset and adhered to from then on.
25. In some cases it may be inappropriate to publish unrounded figures even if there
is a business requirement for them, due to security or data quality concerns – this
should be considered when deciding on a rounding scheme.
Survey Statistics
26. There is often a business requirement to publish results of MOD surveys
unrounded, due to small population sizes and the types of analyses that the
numbers support. It is difficult to apply an overall rounding policy to survey data
as different surveys are based on different sample sizes and different
populations, and will thus have different disclosure issues.
27. Rounding policies for surveys should be agreed on a case by case basis. Where
results of a particular survey are published on a regular basis, a consistent
rounding policy should be applied. Numbers should typically be rounded to 5 or
10 unless there is a business reason to publish unrounded figures.
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28. Survey outputs should be checked for potential disclosure issues, and where
there is concern small numbers should be concealed. Examples of cases where
there is potential for disclosure may include:
a. Surveys where the sample population is easily identifiable
b. Cases where the output includes very small numbers
29. Any branch publishing survey results has a responsibility to decide on a rounding
policy for that survey and ensure that there is no risk of disclosure if publishing
unrounded numbers. Survey reports should include mention of the agreed
rounding policy and any measures that were taken to prevent disclosure.
Search and Rescue Statistics
30. This section on Search and Rescue statistics was added in version 1.1 of this
policy published in July 2010. Search and Rescue statistics were excluded from
the original version of this policy as at the time of publication search and rescue
statistics were due to be ceased.
31. Search and Rescue statistics should be published unrounded. There is no
disclosure risk as they do not involve personal data, and the data are validated at
source so there are no concerns over inaccuracy of the figures. The primary
customers for the statistics are internal MOD customers who have a requirement
for unrounded data for management information purposes – many of the
statistics published include small numbers which would be largely obscured by
rounding.
Other Statistics
32. Statistics not covered by any of the above categories should normally be
rounded to 10 with numbers ending in 5 being rounded to 20.
33. If the statistics in question involve particularly large numbers, then it may be
appropriate to round to a larger number.
34. If there is a requirement to publish unrounded figures, this may be possible
depending on the nature of the data, but you should with check HOB WDS first.
35. You should aim to use the same rounding scheme for all outputs involving that
data type.
Percentages
36. Percentages should be based on unrounded numbers.
37. In cases where percentages are based on particularly small numbers, showing
percentages based on unrounded numbers may present a disclosure risk. If it is
possible to derive from a percentage the exact number of people covered by that
percentage and that number is less than 5, you should take measures to prevent
this. This may involve showing the percentages to less significant figures, hiding
percentages based on small numbers (though you should make sure it is not
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possible to derive these percentages from the sum of the rest), or concealing the
total population size that the percentages are based on.
38. The number of significant figures that percentages should be shown to will
depend on the circumstances. However in most cases it will be appropriate to
use 0 or 1 decimal places.
Consistency
39. When publishing statistics that are already available from another source, figures
should be rounded consistently with the other source where it is known that the
appropriate level of precision of the figures from the other source have been
given professional consideration. If it is felt that statistics published by another
source are being incorrectly rounded, DASA statisticians should consider
contacting the publisher and providing advice on rounding best practice.
Implementation
40. The policy takes effect immediately, and should be applied to all new outputs. It
is recognised that in some cases where regular publications are non-compliant
with the policy, branches may require some time to amend their processes –
where there is a risk of disclosure or breach of confidentiality this should be done
immediately, but otherwise branches should ensure that regular processes are
amended within 3 months of the policy being formally approved.
41. It is the responsibility of Heads of Branches to ensure that their branch’s outputs
are compliant with the policy, and that their staff understand the policy and the
principles of rounding.
42. A PowerPoint presentation will be made available alongside this policy, which
can be used as a quick reference guide and included in staff induction
processes.
43. Customers seeking rounding advice should be advised to follow the appropriate
rounding policy for the data type they are dealing with. The MOD FOI Guidance
Note on Statistical Data includes a paragraph on rounding which suggests that
numbers should typically be rounded to 10, and recommends that people seek
advice from DASA.
44. HOB DASA(WDS) has overall responsibility for this policy, and should be
consulted if there is any confusion over any part of it, or if there is uncertainty as
to how a particular output should be rounded.
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Annex A – Wording to be used when providing unrounded manpower statistics to
internal customers
The following wording should be used when providing unrounded manpower statistics to
internal customers for statistical or research purposes:
These unrounded data are being passed to you to be used for statistical purposes only within the
Ministry of Defence, in accordance with the Data Protection Act 1998: Section 33. Since they
may lead to the identification of individuals, you may not publish them, nor use them in response
to a Freedom of Information Act enquiry, nor in a reply to a Parliamentary Question, nor
otherwise pass them to a third party. You may not use the data for anything other than a
statistical purpose: you may not process these data to support measures or decisions with respect
to particular individuals. For data to use in respect of legal proceedings, please contact DASA
directly.
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Annex B: Rounding Policy for Defence related expenditure data and statistics
This guide outlines the suggested rounding conventions for the type of data and statistical outputs which appear in UKDS Chapter 1
and other outputs produced internally and externally by DASA DESA-DEA. This is not an exhaustive guide and it is advised that if
you are not a ‘subject matter expert’ in this area that you seek advice from Head of DASA DESA-DEA before proceeding. All
published numerical output should be reviewed as they are published to decide whether the appropriate degree of rounding has been
applied, having regard for the considerations of clarity and precision as outlined in the main DASA Rounding Policy.
Data /Statistics
type
Departmental
Resources
MOD Chart of
Accounts data –
RDEL and CDEL
categories
MOD Chart of
Accounts data –
Resource Account
Code level
MOD R&D
expenditure
Industry &
Employment
Estimates of MOD
expenditure within
UK industry
groupings (SIC
code level)
Rounding recommendation
– Internal publication
Rounding
recommendation –
External publication
Rationale
Linked UKDS 2008 tables
To nearest £1M, Inclusive of
non-recoverable VAT at
current prices
As Internal
1.1,1.2,1.3,1.4,1.5,1.6,1.7
Depending on RAC, seek
advice from CFAT,DP&A or
lead policy sponsor via
DASA-DESA-DEA
As Internal
Precedent set elsewhere as data appears at
this level of accuracy and precision in
published MOD accounts which is audited by
NAO.
Level of disclosure and rounding for some
RACs will depend on national security issues.
To nearest £1M, Inclusive of
non-recoverable VAT
As Internal
To nearest £10M, exclusive
of VAT at current prices
As Internal
Level of accuracy and precision is governed
by the published MOD accounts which are
audited by NAO.
Rounding convention follows that set by ONS
in their GERD R&D survey
Level of rounding reflects concerns with
quality, coverage and definitional uncertainties
with the underlying contracts data at SIC
level.
Individual components are rounded
independently which mean that sum totals
may not add up exactly.
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1.1,1.2,1.3,1.4,1.5,1.6,1.7
1.8
1.9/1.9a
Estimated National
defence related
employment
estimates
Estimated
Regional defence
related
employment
estimates
To the nearest 5,000 FTE
To the nearest 1,000 FTE
As Internal
Level of rounding reflects concerns with
quality, coverage and definitional uncertainties
with the underlying data from the Annual
Business Inquiry and internal contracts data.
Individual components are rounded
independently which mean that sum totals
may not add up exactly.
Level of rounding reflects concerns with
quality, coverage and definitional uncertainties
with the underlying contracts data at
region/location level
As Internal
1.10
1.11,1.11a,1.11b
Individual components are rounded
independently which mean that sum totals
may not add up exactly.
Estimated regional
direct MOD
expenditure –
Equipment & Non
Equipment
To nearest £10M, exclusive
of VAT at current prices
Rounding as Internal.
Considered release
on case by case
basis
Level of rounding reflects concerns with
quality, coverage and definitional uncertainties
with the underlying contracts data at
region/location level.
Not published in UKDS
Individual components are rounded
independently which mean that sum totals
may not add up exactly.
Trade
Defence Exports &
Import Deliveries
Balance of
To nearest £1M, at current
prices
To nearest £1M, exclusive of
As Internal
Precedent set elsewhere as data appears at
this level of accuracy and precision in
published in the Annual Report on Strategic
Arms Control.
Level of accuracy and precision previously
agreed at Defence Trade Statistics Working
Group
Precedent set elsewhere as data appears at
As Internal
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1.13,1.14
1.15
Payments: Trade
in Services
International
Defence
International
Defence
expenditure
MOD Operations
and Peacekeeping
costs
Defence
Contracts
Contract values
Annual payments
by contractor
Annual payments
by contract
number
VAT at current prices
this level of accuracy and precision in
published in ONS publication ‘The Pink
Book’.
To the nearest million
currency unit
As Internal
Reproduced from secondary source data –
follows published rounding conventions.
1.20,1.21,1.22
To nearest £1M, Inclusive of
non-recoverable VAT at
current prices
As Internal
Precedent set elsewhere as data appears at
this level of accuracy and precision in
published MOD accounts which is audited by
NAO.
1.19
To nearest £10M, exclusive
of VAT at current prices
Not published
externally without
prior consultation
with DCD. If
published externally,
level of rounding
agreed with DCD
beforehand.
Not published
externally without
prior consultation
with DCD. If
published externally,
level of rounding
agreed with DCD
beforehand.
No external publication due to statutory
exemptions which relate to commercial and
market sensitivities
Not published in UKDS
To nearest £1M, exclusive of
VAT at current prices
To nearest £1M, exclusive of
VAT at current prices
Not published
externally without
prior consultation
9
Internal - Level of rounding reflects concerns
with quality, the underlying contracts data at
contract value level
No external publication due to statutory
exemptions which relate to commercial and
market sensitivities
Published at payment
banding level in UKDS
table1.18/1.18a
Internal - Level of rounding reflects concerns
with quality, the underlying contracts data at
payment level
Not published in UKDS
No external publication due to statutory
exemptions which relate to commercial and
Annual individual
contract payments
at SIC level
To nearest £10M, exclusive
of VAT at current prices
with DCD. If
published externally,
level of rounding
agreed with DCD
beforehand.
market sensitivities
Not published
externally with prior
consultation with
DCD. If published
externally, level of
rounding agreed with
DCD beforehand.
No external publication due to statutory
exemptions which relate to commercial and
market sensitivities
10
Internal - Level of rounding reflects concerns
with quality, the underlying contracts data at
contract number level
Internal - Level of rounding reflects concerns
with quality, coverage and definitional
uncertainties with the underlying contracts
data at SIC level.
Not published in UKDS