The aim of this contribution was to find out whether the concentration of the insurance market can be explained using another insurance or economic indicator. Data published by the Insurance Europe Association was examined. The research method used was correlation analysis. In the countries of Central and Eastern Europe, it was found that the concentration of the insurance market increases with the growth of the share of gross written premium of nonlife insurance in GDP and with the growth of average non-life insurance per capita. On the contrary, in the countries of Western and Northern Europe, it was found that the concentration of the insurance market does not correlate in any way with the share of gross written premium of non-life insurance in GDP or with the average non-life insurance premium per capita. A strong negative correlation was found between the concentration of the non-life insurance market and the total size of the non-life insurance market (expressed as total gross written premium of non-life insurance).