the postcrisis response of regulation coincided with the greater use of quantitative easing. But it is nonetheless helpful to separate them analytically. A decade ago there would have been reason to think that the monetary policy need for increased central bank balance sheets would be shorter term, while the financial stability See “The central bank balance sheet as a policy tool: past, present and future”, by Andrew Bailey, Jonathan Bridges, Richard Harrison, Josh Jones and Aakash Mankodi. Available here. 1  2  All speeches are available online at www.bankofengland.co.uk/news/speeches and @BoE_PressOffice  2  demand would be permanent. That distinction still stands, but the structural drivers of low equilibrium interest rates suggest the use of central bank balance sheets for monetary policy will be more long-lived than had been anticipated. Expansion of central bank balance sheets in response to Covid  Turning to the more recent period, the financial stability and monetary policy drivers of central bank balance sheet expansion were again deeply intertwined. Central banks faced an incipient financial stability shock together with a need for monetary policy to respond to an unprecedented – in scale and speed – economic downturn. But the financial stability emergency differed from previous such events. The problem originated not primarily in the banking system, but in the non-bank sector – among funds, traders and corporates themselves. Central banks activated their traditional tools to inject liquidity into the banks via repo operations, and these played an important part in stabilising conditions.
Where that requires larger purchases of a broader array of assets, it inevitably raises risk management questions for central banks. So, I think the Covid crisis has demonstrated the need to ensure central banks have as many tools as possible in their box, of which expanded purchases of private sector assets is one, but given the issues it raises I would emphasise state contingency here in terms of when some tools may be more appropriate or necessary, given the severity or particular nature of the circumstances at the time. The MPC has considered its prospective approach to QE unwind in recent years, and in June 2018 set out that the balance sheet would be unwound at a gradual and predictable pace, allowing reserves to fall back to a level demanded by banks through their participation in regular repo operations, and once the Bank Rate had risen to around 1.5%, thus creating more headroom for the future use of Bank Rate both up and down. The MPC keeps this approach under review, though I should make clear that it does not seem like an imminent issue in current conditions. But we are looking at the next decade at this conference, so who knows what will happen. We should keep the options to use all our tools as open as possible, so I would conclude that the appropriate policy mix going forwards over a decade may be more nuanced than  5  All speeches are available online at www.bankofengland.co.uk/news/speeches and @BoE_PressOffice  5  previously thought.