The price of EU allowances (EUAs) in the EU Emissions Trading Scheme (EU ETS) fell from almost 30€/tCO2 in mid-2008 to less than 5€/tCO2 in mid-2013. The sharp and persistent price decline has sparked intense debates both in academia and among policy-makers about the decisive allowance price drivers. In this paper we examine whether and to what extent the EUA price drop can be justified by three commonly identified explanatory factors: the economic recession, renewable policies and the use of international credits. Capitalizing on marginal abatement cost theory and a broadly extended data set, we find that only variations in economic activity and the growth of wind and solar electricity production are robustly explaining EUA price dynamics. Contrary to simulation-based analyses, our results point to moderate interaction effects between the overlapping EU ETS and renewable policies. The bottom line, however, is that 90% of the variations of EUA price changes remains unexplained by the abatement-related fundamentals. Together, our findings do not support the widely-held view that negative demand shocks are the main cause of the weak carbon price signal. In view of the new evidence, we evaluate the EU ETS reform options which are currently discussed. •We examine whether abatement-related fundamentals justify the EU ETS price drop.•90% of the variations of EUA price changes remain unexplained.•Variations in economic activity are robustly explaining EUA price dynamics.•Price impact of renewable deployment and international credit use remains moderate.•Reform options are evaluated in the light of the new findings.