 We analyse how boom and bust cycles in both economic activity as well as stock prices are generated by a range of fundamental forces that partly relate also to monetary policy. In particular, we look at the mechanisms through which these cycles arise in response to productivity booms or in response to very low real interest rates. We document that the economy's sensitivity to these developments to fundamental shocks is heightened in periods of low real interest rates and that therefore monetary policy makers should be on the watch out, especially in periods as of now where real interest rates are very low. I think it's great to bring together a lot of people with very different angles on a similar subject area and to learn from each other about the probability of booms arising, about measuring them, about predicting them and that is what I enjoy most, the exchange with colleagues and policy makers alike.