Two data sources are used to measure the Solidarity target.
For the income inequality part of the target the data source is the Family Resources Survey (Households Below Average Income dataset). The unit of measurement is the individual.
Households Below Average Income is a National Statistics dataset owned by Department for Work and Pensions.
For the "increasing total income" part of the target the data source is the Gross Disposable Household Income series, published by the Office for National Statistics.
The Gross Disposable Household Income (GDHI) series published, and owned, by the Office for National Statistics
Data for 2013/14 and previous years are available on the Income and Poverty Statistics website (http://www.gov.scot/Topics/Statistics/Browse/Social-Welfare/IncomePoverty/CoreAnalysis) and on Scotland Performs (http://www.gov.scot/About/scotPerforms/purposes/solidarity).
Future figures will be published annually in June in "Poverty and Income Inequality in Scotland", on the Income and Poverty Statistics website and on Scotland Performs.
New Methodology in 2010
In 2010 a change was made to the way that the Solidarity purpose target was monitored. The Office for National Statistics Gross Disposable Household Income series was introduced as the data source used to monitor the "increase total income" part of the Solidarity target. Prior to this change the Family Resources Survey (FRS) had been used to measure both the income inequality and the "increase total income" parts of the target. The FRS estimates of total household income however, were not in line with GDHI estimates and other sources, mainly because of the equivalisation process applied to the data. The GDHI series was therefore introduced to monitor this part of the target. The FRS continues to be used to monitor the income inequality part of the target.
The Family Resources Survey is a sample survey including approximately 4,500 households in Scotland. The responses of these households are weighted and grossed up to be representative of all private households in Scotland.
Incomes are equivalised (to take into account household composition) using the modified OECD equivalence scale: http://research.dwp.gov.uk/asd/hbai/hbai2010/index.php?page=appendices (Appendix 2 gives more detail)
Once equivalised, weighted and grossed, the total income of every individual is summed to arrive at the total equivalised income figure.
The equivalised, weighted and grossed data are ranked and split into ten evenly sized groups (deciles). The total equivalised income of the lowest three are summed and divided by the Total equivalised income of all deciles, to arrive at the proportion of income received by the lowest 3 deciles.
As the data are from a sample survey all estimates are subject to sampling error. Due to the complex sampling framework the confidence intervals are difficult to calculate and are not currently available.
The Office for National Statistics Gross Disposable Household Income data is the source used to monitor the "increase total income" part of the Solidarity target and is calculated from National Accounts data. GDHI is calculated by adding the balance of "primary income" - essentially income from working or from the ownership of property, minus housing costs; to the balance of secondary income - essentially social benefits received in cash, less taxation.