In order to increase efficiency in production with respect to emissions production, the European trading system with emissions of CO2 has been established at the beginning of this millennium. The impact of this system on participating companies, even after one decade of its functioning, has been questioned many times in published studies. This paper devotes to the analysis of efficiency of steel sectors in the countries of the Visegrad Group, i.e. the Czech Republic, Poland, Slovakia and Hungary. In particular, the fact how efficiently steel producers in the countries are transforming their inputs into ouputs is researched. Moreover, relationships (dependency) between inputs and outputs are identified and discussed. The analysis is made at national level, not at the level of steel producers/companies. The PROMETHEE method is used. To perform the analysis, the data on inputs (number of allowances allocated for free and structure of companies’ size) and outputs (amount of production and CO2 emissions and amounts of production) are used.Keywords: Steel sector, efficiency, PROMETHEE, GAIA, Visegrad four
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