2  BIS central bankers’ speeches  The latter are what Frank Knight, one of the founders of the Chicago school of economics, called “unknown unknowns”. A recent example is the political crisis in Ukraine. However, while this is an example of an “unknown unknown”, it has only limited potential to prevent us from reaching the end of the tunnel.
Ukraine contributes only a quarter of a percent to global economic output. Furthermore, the exposure of European banks to Ukraine is relatively small. According to data from the Bank for International Settlements it stands at about $ billion. A known obstacle that could block our way, on the other hand, is the prolonged period of very low interest rates.