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This in a sense underscores the importance of Tinbergen’s augmented policy rule – that there should be as many policy tools as there are complex sub-systems – when managing a complex system of systems. None of the models so far considers global spill-overs, either through trade or financial channels. Generally-speaking, there is a dearth of macro-economic models which take seriously these international spillovers in an analytically-coherent fashion. Even if modelling this behaviour is over-ambitious in the short-term, there may be merit in improved monitoring of these global flows of financing over time, given their importance for the stability of economies and financial systems. Elsewhere, I have likened this to the creation of “global weather map”. This could be used to track and map the source, scale and nature of cross-border capital flows in close to real-time (Haldane (2012, 2014) and IMF (2013)). Plotting this complex, rapidly-adapting web would be a natural precursor to using it to address “what if” questions. What, for example, would be the impact of a rise in US interest rates on the international flow of funds? The IMF would be the natural guardians of this surveillance-cum-stress-testing machine. (c)  Policy design  Significant changes have been made to the macro-financial policy architecture since the crisis. In general, these frameworks have moved closer towards meeting Tinbergen’s rule of having as many distinct policy tools as there are complex layers in the macro-financial system.