A challenge for this literature is that, as noted by Leeper, Sims and Zha (1996) and Bernanke, Gertler and Watson (1997), most of monetary policy is endogenous, meaning policy authorities move interest rates in response to economic developments, not in spite of them, as I emphasise later. The systematic effects of monetary policy are more complex to characterise. 9  For the monetary policy implications, see for example Broadbent (2013). 6  BIS central bankers’ speeches  to be oscillating around a rate below its historical average. And there have been sharp increases in labour supply caused by peoples’ need to work to help pay down debts and rebuild retirement savings. More recently, net migration has been higher. Most of these shifts are still playing out and haven’t settled into more predictable trends. To make forward-looking policy today in light of such uncertainties about tomorrow, tracking a broad range of indicators helps not just to give a picture of how the economy is evolving in real time but also to update, in a ‘Bayesian’ fashion, an assessment of prospects ahead. In this manner, being data driven isn’t akin to driving by looking in the rear-view mirror but more like adjusting your speed to the terrain ahead. Although different indicators will merit focus at different times, as I highlighted last summer, three types warrant particular attention at present:10 1. The prospects for growth momentum in excess of trend consistent with eliminating spare capacity in the economy;  2.

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