To calculate the average difference in income levels between municipalities, the average income per inhabitant was calculated. To do this the average disposable income was standardised as follows.
The disposable household income is divided by an equivalence factor. The equivalence factor takes into account the advantages of scale which are a consequence of living in a household with several people. The calculation does not include institutions, homes or student households.
In 2004 the average per capita income level for the whole country was 20.4 thousand euro. This is the standardised income of the household to which a person belongs. This is the amount used to calculate the deviations for each municipality and province.