The unece organizes with the financial support of the World Bank

Data collection and compilation of time series

Seasonal adjustment

Conclusions

Introduction

• A survey on seasonal adjustment in 2008

• Challenges with STS were analyzed in 2007 and 2009 via web sites of NSOs on:

• Consumer price index
• Producer price index
• Producer price index for services
• Industrial production index
• Retail trade turnover
• Turnover of services
• Volume of services production
• Wages and salaries

Countries included in the assessment:

• Countries included in the assessment:

• Albania
• Armenia
• Azerbaijan
• Belarus
• Bosnia and Herzegovina
• Georgia
• Kazakhstan
• Kyrgyzstan
• Republic of Moldova

Introduction

• What constitutes international comparability in STS?

• Coverage
• Classifications
• Methodological and computational practices
• Provision of fixed based and/or discrete time series
• Provision of long coherent time series
• Provision of seasonal adjusted series
• Dissemination of documentation

Availability of Time Series

Availability of STS on Services

Availability of STS on Services

• Share of services (incl. trade) in GDP:

• 52% 1996 -> 57% 2008 (in the EECCA countries)

• Lack of data for services

• Problems for estimating GDP

• 8/17 countries publish wages and salaries

• Output indicators rarely produced

• 7 countries publish turnover or volume of services

• Indicators do not cover the whole service sector

• Indicators limited to transport, hotels and restaurants

Availability

Publication Policy Issues

• Almost all countries publish advance release calendars

• A huge step forward in just a few years

• Most countries archive releases to websites

• Time series not easily accessible

• Few countries have a published revision policy

• Metadata have been improved

• Timeliness of releases is often very good

Timeliness

Publication of Metadata

• 15 of 17 surveyed countries provide some methodological information in English

• Countries subscribing to IMF’s SDDS or GDDS have more comprehensive set of metadata

• For statistics not included in SDDS/GDDS

• Very little data for retail trade and services
• Many details regarding production methods not available in English

Publication Methodology

• Revisions are a necessary feature of STS

• Data are rarely published in time series format

• Instead data for a few months is published
• Seasonally adjusted data can only be published as long time series

• Only half of the countries publish indices with a fixed reference period

• Change from previous period should only be calculated from seasonally adjusted data!

Methodology and Comparability

Many have cut-off samples or totals

• Many have cut-off samples or totals

• Over sampling for some countries and indicators?

• Some use registers to reduce sample sizes and increase efficiency

• Register data requires substantial IT resources and implementation of new production methods

• NSOs may have difficulties in accessing registers?
• May provide a solution for developing new statistics?

Compilation Methodology

• Good knowledge of international standards exists

• Significant methodological differences exist:

• price indices, retail trade turnover, wages and salaries

• Some incoherences in definitions

• Definitions of turnover, wages and salaries
• Treatment of VAT, subsidies and delivery costs
• Need to standardize definitions also in the EU

• Almost all countries use internationally comparable classifications for economic activities (ISIC/NACE)

Time Series Methodology

• Production of cumulative data

• Suitable for national use only

• Summarizes development during the current year

• When data are available for April -> information is provided from January to April
• Length of the reference period changes with each release (Jan-Feb > Jan-Mar > Jan-Apr…)

• Cumulative data are usually only additional information, not the only type of data

• A huge step forward: done by a majority of countries