The introduction of the Transmission Protection Instrument is the latest evidence, that the EMU is confronted with unstable markets for government bonds. Based on a parsimonious model of the government bond market, I argue, that this results from the introduction of the euro, which has homogenized government bonds. Now, several easily substitutable bonds are traded at the same time. Investors sort according to return and risk instead of along currencies. This self-selection, however, creates instability in crises. Price convergence and sorting characterized the first decade of the euro, instability the second.
