Analiza rozbieżności danych lustrzanych dotyczących masy towarów w statystykach handlu wewnątrzunijnego

In the research carried out to date by the authors of the article, the assessment of the quality of mirror data in the exchange of goods between European Union (EU) countries was based on the value of goods. A similar approach is applied by many researchers. The aim of the research discussed in the article is to assess the quality of data relating to intra-EU trade based on not only the value, but also on the quantity of goods. The analysis of discrepancies in data relating to trade between EU countries, with a particular emphasis on Poland, was based on selected research methods known from literature. Both the value-based and the quantitative approach constitute the authors' contribution to the development of research methodology. Data quality indicators were proposed and data pertaining to the weight of goods were used. Information on trade in goods between EU countries in 2017 obtained from Eurostat's Comext database was analysed. The research relating to the dynamics also covered the years 2005, 2008, 2011, and 2014. The results of the analysis demonstrated that the total share of export of goods from Poland to a given country within the EU is different for data expressed in value (value of goods) and in quantity (weight of goods). Therefore, both approaches should be applied in the study of the quality of mirror data.