During the POLPAN Seminar on February 6th, 2020, Professor Zbigniew Sawinski (Institute of Philosophy and Sociology, Polish Academy of Sciences) presented a paper entitled “Use of common and country-specific classifications in the harmonization of cross-country surveys.”


The harmonization of cross-country survey data is usually based on classifications common to countries. Country-specific classifications are only used if the common classification does not apply, as in the case of territorial divisions, which are different in each country. However, each variable included in cross-country comparisons has, in a sense, a ‘country-specific’ component. This suggests that extending the use of the country-specific classifications to other variables may broaden the scope of harmonization proposals.

The advantages and disadvantages of using country-specific classifications in the harmonization of data from different countries is illustrated by education in European Social Survey. Although school systems are deeply rooted in national tradition, harmonization in the ESS, like in many other surveys, boils down to mapping the educational achievements in each country (i.e. source variables) to a common target variable – usually the ISCED classification. When the loss of information associated with this mapping varies from country to country, conclusions about countries may be distorted (e.g. conclusions about the actual impact of education on opinions and attitudes). Such distortion can be avoided by using country-specific classifications that better match school systems and minimizes information loss. Another advantage of using country-specific classifications is to draw the attention of data users from around the world to some specific mechanisms that are fundamental to understanding the role of education in a given country, but usually not included at the general level of standard international classifications (e.g. private vs. public schools, academic vs. vocational tracks). The examples from the ESS survey provide arguments that the additional inclusion of country-specific classifications may extend the scope of harmonization proposals based on a common classification.

Key words: Cross-country harmonization, Country-specific classification, Information loss, ISCED (International Standard Classification of Education), European Social Survey

Prof. Sawinski’s article related to the Seminar topic can be found at: