This paper analyses two factors which may cause cyclically-adjusted budget balances to give a misleading picture of underlying fiscal trends. It first explores the implications of recent large asset-market related fluctuations in government revenues for the measurement of structural budget balances. And second, it reviews the impact of the increased recourse to stopgap "one-off" measures to control deficits. The results confirm that since the late 1990s revenues have been more buoyant than would have been warranted by the registered rate of nominal output growth and the impact of tax measures. The study suggests that from 1995 to 2000 the average contribution of "unwarranted" revenues to year-to-year changes in cyclically-adjusted budget positions ranged from negligible to around ½ per cent of GDP, the main countries affected being the United States, the United Kingdom, France and some Nordic countries. Conversely, the subsequent decline in tax receipts has been sharper than could ...