Statistical uses of classifications: constraints and examples

Jean Lienhardt

Description

Classifications play an essential role in statisticians' everyday activity. In particular, classifications of activities and products have many practical uses—often implicit—in statistical operations. In reviewing these applications, we point out the reasons why adjustments and updates are needed when classifications change. Moreover, the implementation of new classifications, along with the necessary backcasting and extrapolations, takes place within a multi-faceted and constraining regulatory framework.

Sujets

• INSEE
• Économie

Informations

• Publié par: insee
• Nombre de lectures: 33
• Langue: English
• Poids de l'ouvrage: 1 Mo

Extrait

Statistical uses of classifications:
1constraints and examples
! Jean Lienhardt*
Classifications play an essential role in statisticians’ everyday activity. In particular, classifications of activities and
products have many practical uses—often implicit—in statistical operations. In reviewing these applications, we point
out the reasons why adjustments and updates are needed when classifications change. Moreover, the implementation
of new classifications, along with the necessary backcasting and extrapolations, takes place within a multi-faceted and
constraining regulatory framework.
lassifications of activities and The APE code (principal c products are an integral part of economic activity) can
the basic organization of statistical serve as identifier in
sources. This article examines several business statistics
examples.
France’s official statistical service is
characterized by heavy interdependent
Classifications of activities operations, particularly in the field
and products are used of business statistics. We thus
to define survey coverage need to define relevant criteria for
and statistical indicators identifying statistical units and their
aggregations.
The “sectoral” eU statistical
regulations (i.e., concerning individual For this purpose, one of the most
economic activities) use nAce to Detail from cover of French Classifications of significant information items
Activities and Products (NAF Rev. 2 / CPF Rev. 2)define their scope of application. The associated with statistical units
change in data repository from one in individual data files is the APe
nAF version to the next has two code. The same is true of certain
immediate consequences: aggregated files: the APe code often
serves as the main identifier for a
– A technical consequence: the stratum or aggregate. We therefore Classifications are used
transposition of the regulation within aim to systematically check the to select samples
a constant scope code in databases and registers.
This verification determines the In business statistics, n AF is the – A political consequence: the
quality of information exchanges paramount criterion for most stratified negotiation on extensions and
between statistical files directly samplings. All registers and survey restrictions of coverage entailed by
involving aggregates—for example, launch tools must therefore be the change.
in “Intermediate enterprise immediately adjusted to meet the
Systems” (Systèmes Intermédiaires standards of a new classification. In practice, one can adjust the scope
d’entreprises: SIes).This notably concerns the French of coverage of statistical sources by
business register (SIRene) and related setting up new surveys or maintaining
registers, the survey launch files, and existing surveys for the sake of
sampling frames. The change in data continuity.
repository requires at least an update
A secondary consequence is of these basic tools.
the redefinition of the spheres of
competency of statistical agencies, Beyond, there may be challenging
* Jean Lienhardt is coordinator of Projects for also based on classifications. In France, methodological consequences. For
changes in Activity classifications at InSee.
this involves transfers of competency continuous surveys, which call for 1. o riginally published as “Les usages
statistiques des nomenclatures: contraintes et between ministerial statistical offices partial sample replacement, it is
exemples,” Courrier des statistiques (French
(Services Statistiques Ministériels: important to ensure consistency
series), no. 125, nov.-Dec. 2008, pp. 77-84,
SSMs). between samples. http://www.insee.fr/fr/ffc/docs_ffc/cs125m.pdf.
courrier des statistiques, english series no. 15, 2009 69
Source: InSeeJean Lienhardt
The APE code is used in
Box 1: Using NAF in automatic codingmany ways in statistical
production processes, in Many statistical operations use coding throughout 2008 with the headings
the application “engines” tools to transform respondents’ plain- collected in the declaration packages
language declarations of APe codes filed for new businesses (as the self-themselves
into classification codes. reported headings are not those of
the classification). The census and
A few examples: continuous labor-force survey will use Two variables are generally involved:
similar knowledge databases, compiled – principal economic activity (Activité
in summer 2008.– In the Annual enterprise Survey Principale exercée: APe) coded with
nAF(enquête Annuelle d’entreprise: eAe), For occupation coding, SIcoRe serves
– occupation coded with the to code declarations of occupation APe codes are determined from the
“occupations and Socio-occupational gathered in surveys or employers’ data gathered. The classification
categories” (Professions et catégories Annual Declarations of Payroll Data change requires a new algorithm for Socioprofessionnelles: PcS) system. (Déclarations Annuelles de Données
constructing the code. Sociales: DADS). SIcoRe is used in
InSee has developed a general- two ways. First, we include it in the
purpose automatic coding software – In many applications, the APe code post-collection processing sequence
program called SIco Re (French for “large” surveys and administrative enters into the definition of quality
acronym for “c omputerized System files. Second, we install it in interviewers’ criteria: minimum representativeness
for coding Survey Responses”). Pcs for “light-weight” surveys.
for a stratum of the Industrial SIcoRe uses “knowledge databases” Automatic processing is supplemented
Production Index (IPI); quality targets containing plain-language headings by operations performed by specialized
for the compilation of summary and their associated codes. It also teams at InSee Regional offices.
uses “ancillary variables,” i.e., statistics; quantitative criterion
information from the same documents For the population census, the in regulated operations to prepare
as the variable to be coded (SIRene continuous labor-force survey, and structural statistics. The classification
“declaration packages” filed by new surveys using the “common core” of update entails an adjustment of quality
enterprises, questionnaires, and so household surveys (Tronc c ommun
thresholds and criteria. on). These variables facilitate code des enquêtes auprès des Ménages:
determination thanks to decision tables, TcM), SIcoRe incorporates up to
which are sets of specific logical rules – The APe code is used recurrently fourteen ancillary variables, of which
for the variable to be coded. two are based on nAF:in coding-related questions: either
– the APe code at the most detailed directly, if the question concerns the
As nAF is used—directly or level of the classification (census,
APe heading in plain language, or
indirectly—in these coding operations, labor-force survey)
indirectly if the APe code is used as the effects of the classification change – a n AF2 variable reflecting the
an ancillary variable to code other are significant. divisions of the new classification
variables—for example, to determine (available in surveys using the TcM).
For APe coding, we need to adapt the socio-occupational categories (PcS)
knowledge databases to the headings The n AF change therefore requires in household surveys. Box 1 describes
and codes of the new classification. us to adapt—and, in most cases, to the procedures, which rely on SIcoRe
Such files are used for the business rewrite—the decision tables that use
software. The classification change register (SIRene ), the population these two variables.
naturally requires a redesign of the census, and the continuous labor-force InSee also transmits results under
related files (knowledge bases), a survey (eec). the ISco classification (see articles by
substantial task. In early 2008, we incorporated the Brousse and Torterat). The PcS-ISco
nAF Rev. 2 headings into the SIRene conversion table uses the detailed nAF
knowledge databases. We assigned breakdown, nAF2, and enterprise size.
new codes to the headings already The table, as well, was redesigned in
determined. We enriched these files 2008.Classifications are a tool
of choice for disseminating
and analyzing results
In See cannot, of course, confine references. Indeed, eU regulations APe often exhibit similar economic
itself to releasing raw data require Member States to disseminate behavior. n AF and the “summary
files—if only because of statistical data under the new categories. economic classifications” (see article
confidentiality rules. We therefore The purpose of this constraint is to by Madinier) were built specifically
prepare statistical results tailored to promote comparability and quality of to allow insightful descriptions of the
the classification categories. It is the workings of the French economy. In results.
role of dissemination applications to this field as well, the classification
construct these results. Databases and The APe variable is also a hi