Statistical Methods, Standards and Guidelines
24 2.6 REVIEW AND REBASING PROCEDURES
2.6.1 Review of Information Products
Standard 2.6.1: MDAs, LGAs and other stakeholders are responsible for the quality of
information that they disseminate and must institute appropriate content/subject matter,
statistical, and methodological review procedures to comply with NBS and MDAs, LGAs and
other stakeholders.
The guidelines for this standard are: Guideline 2.6.1.1: Conduct a subject-matter review of all information products that present a description or interpretation of results from the survey, such as analytic reports or “briefs.” Select reviewers with appropriate expertise in the subject matter, operation, or statistical program discussed in the document. Among the areas that reviewers should consider are the following:
a) Subject-matter literature is referenced in the document appropriately;
b) Information is factually correct; and
c) Information is presented clearly and logically, conclusions follow from analysis, and no
inconsistent findings are ignored.
Guideline 2.6.1.2: Conduct a statistical and methodological review of all information products. Select reviewers with appropriate expertise in the methodology described in the document. Among the tasks that reviewers should consider are the following:
a) Review assumptions and limitations for accuracy and appropriateness;
b) Ensure that appropriate statistical methods are used and reported;
c) Review calculations and formulae for accuracy and statistical soundness;
d) Review data and presentations of data (e.g., tables) for disclosure risk;
e) Review contents, conclusions, and technical (statistical and operational areas) recommendations to ensure that they are supported by the methodology used; and
f) Ensure that data sources and technical documentation, including data limitations, are included or referenced.
Statistical Methods, Standards and Guidelines
25 Guideline 2.6.1.3: Review all information products that will be disseminated electronically for compliance with existing policies and legislations governing statistical activities in the country for easy accessibility. Ensure that any pro duct that is disseminated via special software is tested for accessibility and interpretability prior to dissemination.
Guideline 2.6.1.4: Rebase and update i nformation products with new and current data produced from survey and routine data.
Guideline 2.6.1.5: Review and harmonize information products using common standards and levels of classification such as ISIC, SNA, etc. Avoid aggregating information products using different standards and classifications before harmonizing them. If it is necessary t o customize to local conditions or branch out of main classifications, maintain the link to international standard.
2.7 DISSEMINATION
2.7.1 Information Release Standard 2.7.1: MDAs, LGAs and other stakeholders must release information intended for the general public according to a dissemination policy that provides for equivalent, timely access to all users and provide information to the public about the MDAs, LGAs and other stakeholders‟ dissemination policies and procedures including those related t o any planned or unpredicted data revisions.
The guidelines for this standard are:
Guideline 2.7.1.1: Dissemination procedures for major information products may include the
following:
a) Develop release calendar and method for the release of information pr oducts and
services;
b) Inform targeted stakeholders; and
c) Ensure equal and timely access to all users.
Guideline 2.7.1.2: Protect information against any unauthorized pre -release, and release information only according to established release procedures.
Statistical Methods, Standards and Guidelines
26 Guideline 2.7.1.3: If revisions to estimates are planned, establish a schedule for expected revisions, make it available to users, and identify initial releases as preliminary.
Guideline 2.7.1.4: Establish a policy for handling unscheduled corrections due to previously unrecognized errors. The policy may include threshold criteria (e.g., the correction will change a national level total value by more than one percent or a regional value by more than five percent) identifying conditions under which data will be corrected and re-disseminated.
Guideline 2.7.1.5: When information products are disseminated, provide users with access to
the following information:
a) Definitions of key variables;
b) Source information, such as a survey form number and description of methodology used
to produce the information or links to the methodology;
c) Quality-related documentation such as conceptual limitations;
d) Variance estimation documentation;
e) Time period covered by the information and units of measure;
f) Point of contact to whom further questions can be directed;
g) Software or links to software needed to read/access the information and installation/operating instructions, if applicable;
h) Date the product was last updated; and
i) Standard dissemination policies and procedures.
2.7.2 Documentation and Archiving Standard 2.7.2: MDAs, LGAs and other stakeholders must produce survey documentation that includes those materials necessary to understand how to properly analyze data from each survey, as well as the information necessary to replicate and evaluate each survey‟s results. Survey documentation must be readily accessible to users, unless it is necessary to restrict access to protect confidentiality.
The guidelines for this standard are:
Guideline 2.7.2.1: Survey system documentation (metadata) includes all information
necessary to analyze the data properly. It includes the following:
i.
Survey instruments;
Statistical Methods, Standards and Guidelines
27
ii.
Description of variables used to uniquely identify records in the data file;
iii.
Description of the sample design, and sampling unit identifiers to be used for
analysis;
iv.
Definitions of all variables, including all modifications;
v.
Data file layout;
vi.
Descriptions of constructed variables on the data file that are computed from
responses to other variables on the file;
vii. Description of sample weights, including adjustments for non-response and benchmarking and how to apply them;
viii. Description of how to calculate variance estimates appropriate for the survey design;
ix. Description of all editing and imputation methods applied to the data (including evaluations of the methods) and how to remove imputed values from the data;
Guideline 7.2.2: To ensure that a survey can be replicated and evaluated, the MDA, LGA and
a stakeholder‟s internal archived portion of the survey system documentation, at a minimum,
must include the following:
i.
Survey planning and design decisions, including the NBS Information Collection
Request package;
ii.
Field test design and results;
iii.
Selected sample;
iv.
Sampling frame;
v.
Justifications for the items on the survey instrument, including why the final items
were selected;
vi.
All instructions to respondents and/or interviewers either about how to properly
respond to a survey item or how to properly present a survey item;
vii. Description of the data collection methodology;
viii. Sampling plan and justifications, including any deviations from the plan;
ix.
Data processing plan specifications and justifications;
x.
Final weighting plan specifications, including calculations for how the final weights
were derived, and justifications;
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xi.
Final imputation plan specifications and justifications;
xii. Data editing plan specifications and justifications;
xiii. Evaluation reports;
xiv. Descriptions of models used for indirect estimates and projections;
xv. Analysis plans;
xvi. Time schedule for revised data; and
xvii. Documentation made publicly available in conjunction with the release of data.
Guideline 2.7.2.3: For recurring surveys, produce a periodic evaluation report, such as a methodology report, that itemizes all sources of identified error. Where possible, provide estimates or bounds on the magnitudes of these errors; discuss the total error model for the survey; and assess the survey in terms of this model.
Guideline 2.7.2.4: Retain all survey documentation according to appropriate Tanzania records disposition and archival policy and law.
Statistical Methods, Standards and Guidelines
29 PART II: STANDARD CLASSIFICATIONS IN STATISTICAL PRODUCTION
3.0 THE INTERNATIONAL STANDARD INDUSTRIAL CLASSIFICATION OF ALL ECONOMIC ACTIVITIES (ISIC)
ISIC is the international reference classification of a coherent and consistent structure of economic activities based on a set of internationally agreed concepts, definitions, principles and classification rules.
ISIC structure
The hierarchy in ISIC consists of:
Section (one letter code)
Division (two digits code)
Group (three digits code)
Class (four digits code)
Objective and use of ISIC ISIC is intended to be a standard classification of productive activities. Its main purpose is to provide a set of activity categories that can be utilized for the collec tion and presentation of statistics according to such activities. Therefore, ISIC aims to present this set of activity categories in such a way that entities can be classified according to the economic activity they carry out.
It provides a comprehensive framework within which economic data can be collected and reported in a format that is designed for purposes of economic analysis, decision -taking and policy-making. The classification structure represents a standard format to organize detailed information about the state of an economy according to economic principles and perceptions
The ISIC has widely being used both nationally and internationally in classifying data according to kind of economic activity in the fields of production, employment, gross do mestic product and other statistical areas. ISIC is a basic tool for studying economic phenomena, fostering international comparability of data, providing guidance for the development of national classifications and for promoting the development of sound national statistical systems.
Statistical Methods, Standards and Guidelines
30 Classification rule The classification is used to classify statistical units, such as establishments or enterprises, according to the economic activity in which they mainly engage. At each level of ISIC, each statistical unit is assigned to one and only one ISIC code,
The set of statistical units that are classified into the same ISIC category is then often referred to as an industry, such as “the furniture industry”, which would refer to all units classified in ISIC division 31 (Manufacture of furniture)
This standardized categorization or subdivision of the complete set of producing units in an economy makes ISIC an important tool for socio-economic statistics that need to be arranged in accordance with the productive system of the economy.
The individual categories of ISIC have been aggregated into the following 21 sections:
A 01–03
Agriculture, forestry and fishing
B 05–09
Mining and quarrying
C 10–33
Manufacturing
D 35
Electricity, gas, steam and air conditioning supply
E 36–39
Water supply; sewerage, waste management and remediation activities
F 41–43
Construction
G 45–47
Wholesale and retail trade; repair of motor vehicles and motorcycles
H 49–53
Transportation and storage
I 55–56
Accommodation and food service activities
J 58–63
Information and communication
K 64–66
Financial and insurance activities
L 68
Real estate activities
M 69–75
Professional, scientific and technical activities
N 77–82
Administrative and support service activities
O 84
Public administration and defence; compulsory social security
P 85
Educations Q 86–88 Human health and social work activities R 90–93 Arts, entertainment and recreation S 94–96 Other service activities
Statistical Methods, Standards and Guidelines
31 T 97–98 Activities of households as employers; undifferentiated goods and services producing activities of households for own use U 99 Activities of extraterritorial organizations and bodies
3.1 THE CLASSIFICATION OF INDIVIDUAL CONSUMPTION BY PURPOSE (COICOP) COICOP is one of the functional classifications in the UN 1993 System of National Accounts (SNA93). It is used to classify individual consumption expenditures of three institutional sectors, namely households, Non-Profit Institutions Serving Households (NPISHs) and Government.
COICOP is described as a “functional” classification because it categorizes consumption expenditures according to their primary “functions” – in the sense of “purposes” or “objectives”; for example, housing, medical, transport, recreation and education.
Detailed structure 01-12 - Individual consumption expenditure of households 01 - Food and non-alcoholic beverages 02 - Alcoholic beverages, tobacco and narcotics 03 - Clothing and footwear 04 - Housing, water, electricity, gas and other fuels 05 - Furnishings, household equipment and routine household maintenance 06 - Health 07 - Transport 08 - Communication 09 - Recreation and culture 10 - Education 11 - Restaurants and hotels 12 - Miscellaneous goods and services 13 - Individual consumption expenditure of Non-Profit Institutions Serving Households (NPISHs) 14 - Individual consumption expenditure of general government
Statistical Methods, Standards and Guidelines
32 3.2 TANZANIA STANDARD CLASSIFICATION OF OCCUPATIONS (TASCO) Tanzania Standard Classification of Occupations (TASCO) provides a systematic classification and codification structure for the civilian working population of the United Republic of Tanzania. TASCO has been fashioned after the International Standard Classification of Occupations, ISCO-1988, compiled by the Internat ional Labour Office, ILO Geneva which is the revised edition of ISCO -68. This adaptation has been done to ensure intern ational and regional comparability of reporting and analysis of statistical data relating to occupations, manpower, population census, etc.
TASCO has been closely aligned with ISCO -88 to ensure international and regional comparability of statistical data . To maintain continuity with the country's past statistical data, based as it is on the ISCO -68, the main text of TASCO for each Major Group gives corresponding ISCO-68 Codes for titles included in the TASCO. The expanded Index, which includes all Base, A lternate and Related Titles of this Classification, will help coders, enumerators, and users of TASCO in the location, classification and codification of all occupations in the country.
Objective of TASCO TASCO has been designed for the proper classification of the collected data of all civilian occupations in the country's labour force and to ensure its convertibility into the international standard.
TASCO, as also ISCO-88, differs from the ISCO-68 in the following aspects:
i. A new level of aggregation, c alled Sub-Major Groups, has been created between those represented by Major and Minor Groups in ISCO-68. ii. The basis of occupational classifications, in the ISCO-68, was according to type of work performed. TASCO and ISCO -88 occupational classifications are based on "Skill requirement" criterion, reflected in the skill level and skill specialisation of various occupations. iii. As a result of introduction of a new level of aggregation, viz sub-major groups , the occupational code structure consists of six (6) digit s, instead of five (5) digits of ISCO - 68; thus:-
Statistical Methods, Standards and Guidelines
33 Major Groups are of one (1) digit, the extreme left numeral, at 'thousand' point of the four digits before the decimal point; Sub-Major Groups consist of two (2) digits, the left two numerals, at 'thousand' and 'hundred' points, of the four-digit numbers before the decimal point; Minor Groups consist of three (3) digits, the left three numerals, at 'thousand' 'hundred' and 'ten' points, of the four-digit numbers before the decimal point; Unit Groups consist of four (4) digits, all the four numerals left of the decimal point; and Occupational Categories consist of six (6) digits, all the four (4) numerals left of the decimal point plus the two (2) numerals right of the decimal point.
Example 2143.40 Instrument Engineer, Electrical;
Major Group is indicated by '2', one digit at the thousand' point;
Sub-Major Group is indicated by '21', two digits at 'thousand' and 'hundred' points; Minor Group is indicated by '214', at 'thousand', 'hundred' and 'ten' points; Unit Group is indicated by '2143', all the four numerals left of the decimal point; and
Occupational category is indicated by 2143.40, i.e. all the four numerals, viz '2143' left of the decimal point plus two numerals, viz.40 on the right side of the decimal point.
Basic Approach and Classification Criteria i. TASCO provides a structure for the classification of all civilian occupations in the country's labour force. Occupational categories are, thus, the smallest segment of work which is specifically identified, classified and codified in the TASCO. At this detailed level, an occupation is a set of jobs which involve the performance of a similar or common, but not necessarily identical, set of tasks all over the country.
An occupation, for the purpose of this classification, covers various jobs similar in their main tasks, and held by individual workers, all over the country, and in various establishments and industries, but workers may perform one or more of the different possible combinations or breakdowns of the set of tasks described in the occupational
Statistical Methods, Standards and Guidelines
34 definitions of ISCO -68, shown against TASCO occupational titles, under its Unit Groups. Workers, in a number of establishments and industries, and whose principal tasks are similar, are considered to be sharing the same type of job; and the workers, in a particular establishment, performing identical principal tasks, are considered to be manning the same type of positions. A position , in any given establishment, is a set of tasks performed by one indi vidual. Therefore, in a given establishment, there will be as many positions as are workers employed therein. In practice, positions are normally distinguished from one another by minor differences in duties, level of responsibility for supervision, and other particularities, e.g. wages and division of labour.
ii. ISCO-68 had classified occupations according to the type of work performed which was reflected in different ways, such as occupations occurring in the same field/discipline (e.g. physical sciences, l ife sciences); those concerned with the same subject -matter (e.g. Chemists, Physicists, Biologists, Agronomists); and those of workers executing similar processes (e.g. metal platers and coaters), operating similar equipment (e.g. motor vehicles), performing similar services (e.g. waiters, bartenders) and fabricating similar articles (e.g. watch, clock and precision instrument makers).
iii. In TASCO, the classification criteria is based on the requirements imposed upon workers by the tasks and duties of their occupations reflected in:
(a) the knowledge and proficiency needed for performing physical and mental activities of the prescribed tasks and duties; (b) the knowledge of working principles, methods and techniques and characteristics of materials and equipment used; and (c) the ability to react adequately to various work situations and demands.
iv. The above technical requirements depend on the skill requirements of an occupation. Skill may be defined as the ability of an individual worker to perform a set of tasks or to fulfil the technical requirements of an occupation. Thus, for the classification of jobs into occupation and of occupations into Unit Groups, skill requirements provide the similarity criterion for sets of tasks in the group structure of TASCO. The foc us is on the skill required to carry out the tasks and duties of an occupation and not on whether a worker,
Statistical Methods, Standards and Guidelines
35 having a particular occupation, is more or less skilled than another worker in the same occupation. iv. The `skill requirement' criterion, used in TASCO, has two dimensions, viz (a) skill level and (b) skill specialisation.
(a) The skill level of an occupation is a function of the complexity and range of the tasks
involved. The greater the complexity and wider the range of the set of tasks, the higher
the s kill level of an occupation. An occupation that involves more complex tasks than
another will require a higher skill level. An occupation which requires the performance of
a wide range of tasks has a higher skill level than an occupation which requires the
performance of a sub -set of those same tasks. But, complexity of task is more important
than mere range of tasks in determining the skill level, since complexity of tasks indicates
the degree of proficiency, the level of knowledge, and the quality and cha racter of the
response required to accomplish such tasks.
(b) The skill specialisation of an occupation is a function of (i) the field of knowledge required (viz. the subject-matter essential to the performance of tasks), (ii) tools, equipment and work aids u sed (e.g. plant, machinery, hand -tools); (iii) materials worked on or with (such as extracted, processed, refined or manufactured), and
(c) Goods produced or services provided in relation to the tasks performed.
From the above, it can be deduced that:- the greater the range and complexity of the set of tasks involved, the greater the duration and amount of (i) formal education; (ii) on -the-job training, and (iii) previous experience required for the satisfactory performance of the set of given tasks; but in some case, innate strength, abilities, appropriate work-experience, coupled with thorough on -the-job training, may equip a worker with the needed skills, or a part of them, for the successful performance of the set of tasks. In Tanzania, quite often, skill s are acquired through informal training and work - experience.
3.3 THE SYSTEM OF NATIONAL ACCOUNTS (SNA) The System of National Accounts (SNA) is the internationally agreed standard set of recommendations on how to compile measures of economic activity. Th e SNA describes a
Statistical Methods, Standards and Guidelines
36 coherent, consistent and integrated set of macroeconomic accounts in the context of a set of internationally agreed concepts, definitions, classifications and accounting rules.
The SNA provides an overview of economic processes, recording how production is distributed among consumers, businesses, government and foreign nations. It shows how income originating in production, modified by taxes and transfers, flows to these groups and how they allocate these flows to consumption, saving and investment. Consequently, the national accounts are one of the building blocks of macroeconomic statistics forming a basis for economic analysis and policy formulation.
Objective and Uses of the System of National Accounts (SNA) The main objective of the SNA is to provide a comprehensive conceptual and accounting framework which can be used to create a macroeconomic database suitable for analyzing and evaluating the performance of an economy. The existence of such a database is a prerequisite for informed, rational policy-making and decision-taking.
Accounts and their corresponding economic activities
The sequence of accounts
Current accounts These accounts record the production of goods and services, the generation of incomes by production, the subsequent distribution and redistribution of incomes among institutional units, and the use of incomes for purposes of consumption or saving.
Production account The production account records the activity of producing goods and services as defined within the System. Its balancing item, gross value added, is defined as the value of output less the value of intermediate consumption and is a measure of the contribution to GDP made by an individual producer, industry or sector. Gross value added is the source from which the primary incomes of the System are generated and is therefore carried forward into the primary distribution of income account. Value added may also be measured net by deducting consumption of fixed capital.