General government spending and revenues are highly sensitive to economic cycles and specific events (e.g. privatisations). In turn, government revenues (particularly tax revenues) tend to decline during economic downturns, at the same time as public spending may increase given that more people become unemployed and qualify for social assistance or unemployment benefits. On the other hand, during upturns, public accounts improve, as tax revenues rise and the number of those receiving social benefits usually declines. Analysing indicators that are not influenced by temporary fluctuations helps policy makers identify the underlying trend of fiscal policies associated with long-term public finance sustainability. The structural fiscal balance aims to capture these trends in order to assess fiscal performance. Estimating the structural balance requires calculating the structural and cyclical components of both the fiscal balance and output or potential GDP (i.e. the economy working at full capacity).