It is a way of defining the shape of the bell-curve for income distribution - whether the tails are long; how skewed the peak is; and how high the peak actually is.
Today's report from the Joseph Rowantree foundation indicates that income distribution is at the most inequal for the past 40 years puts the lie to the tinkering that Gordon Brown has been redistributionist. It is true that much of what he has done has benefited the very worst off, but through means testing, minor increases in benefits and vicious increases in indirect taxes the poorest have fallen back, rather than climbed.
According to the Scottish Executive website, the Scottish Gini coefficient has been relatively steady, at least until 2005 (usual caveats apply).
Whilst UK wide up to 2006 it was increasing.
The message is simple: Labour have failed in their simple socialist promises, due to Blair and Brown's fixation with the nouveau riche and the aspirant champagne socialists who sit as MPs or act as advisers or special advisers to Labour, and who were formerly known as the Conservative Party.
Thatchers legacy was to shift the centre of politics so far to the Right. She must be smiling with delight at the blind way in which Labour have allowed her policies to continue. Somehting I see everyday, when I prepare Tax Returns.
The challenge for the Scottish Government is to reduce the disparity (in so far as it is under its control) without affecting business growth and income generation. Or is that too much to hope for?