Capital requirements that increased with the rate of  BIS Review 39/2009  5  growth of balance sheets, or some measure of incipient stress. Variable margin requirements on the terms of credit provided to financial, or even real-economy, borrowers. A fourth big question is whether the chosen instrument(s), whatever it is, could be operated by rules or would require an element of top-down judgment. On that, I am inclined to the view that our community is unlikely to be able to write down a suitably robust rule. I have two reasons for that. One draws a parallel with monetary policy. The history of monetary policy, not least in this country, is littered with failed attempts to design an optimal rule, giving way to efforts to constrain the discretion of policymakers making judgments. I cannot see why we would be any better at developing rules for financial stability. As the structure of the financial system evolved, we would need to adapt the rule and would probably fail to spot the need to do so. But there is also something about the nature of financial stability problems that makes “rules” implausible to me. In the upswing of the credit cycle, there is often a collective-action problem. Even though individual banks may perceive risk as underpriced, not knowing for sure whether or when the party will end they hesitate to step off the rollercoaster for fear of damaging their business franchise.
Stability in the elemental sense I have described was profoundly threatened last autumn – when the universal crisis of confidence triggered by Lehmans’ failure tore the fabric of international commerce. That stability has been sustained owes everything to governments stepping in, effectively being prepared to borrow from the future in order to prop up the banking system now. In that sense, we are, of course, “beyond Financial Stability”, insofar as, ordinarily, we would regard instability as a state of affairs that requires such support. The Turner Report rehearses the analysis of how we got to that point. It rightly places weight on the baleful effects of persistent and cumulative global current and capital account imbalances. I dearly wish that the international authorities had taken on board the lessons from the 1990s EME crises about the vital importance of monitoring, and where necessary managing, national balance sheets – for large countries as well as EMEs. It is striking, however, that other analysts, including recently from the IMF, are starting to play down the part played by the international monetary system. I do not go along with that. There can  BIS Review 39/2009  1  surely be no disputing that macroeconomic imbalances have mattered greatly to the crisis, as they contributed to the build up of debt and, through the compression of risk-free rates and risk premia, the appreciation of asset prices. But in acknowledging that, we do not have to claim that of themselves such imbalances lead inevitably to financial instability.