The lack of adequate banking regulation by supervisors and flawed assessment of risk by financial institutions over the past several years has proved extremely costly. We estimate that the level of global output declined by a cumulative 2.4 per cent between the onset of the crisis triggered by the collapse of Lehman Brothers and the first quarter of 2009, with a decline of 4 per cent in the OECD economies over the same period. This is equivalent to a loss of roughly $850 billion relative to what was then considered potential output. We estimate that government debt levels in the OECD economies have risen by about 25 per cent in aggregate, entailing many years of higher tax burdens to come, a rise in long-term real interest rates and lower levels of income-generating wealth. The level of employment in the OECD economies declined by 2.2 per cent between the second quarter of 2008 and the second quarter of 2009, and we expect a further 2.5 million people will lose their jobs in the OECD economies by early 2010. While we expect growth to resume by the end of this year in most countries, the level of output in the OECD will remain permanently lower than was expected fifteen months ago. The degree of scarring in individual economies depends on the extent to which lenders underestimated risk before the crisis and the recent rise in the economy's government debt burden. This is discussed in greater detail in a note on pp. 36–8.