1. Department of Statistics and Social Policy, University of Agriculture in Krakow, al. Mickiewicza 21, 31-120 Kraków, Poland
2. Faculty of Economics, West Pomeranian University of Technology, al. Piastów 7, 70-310 Szczecin, Poland
3. Administrative and Economic Department, University of Applied Sciences in Tarnow, ul. Mickiewicza 8, 33-100 Tarnów, Poland