The paper refers to the Prebisch–Singer (PS) hypothesis. The first section presents the hypothesis itself along with its theoretical explanations and a review of research on its legitimacy. The next section describes trends in TOT in years 2000–2011 for developed, developing and transition economies. At the end authors included results of econometrical research, testing for the PS hypothesis and other internal factors affecting TOT. The results did not confirm the PS hypothesis, but they supported assumptions
referring to other factors.