Income inequality in Scotland - and the rest of the UK - was low and stable throughout the 1960s and 1970s.

Then came the 1980s. De-industrialisation and technological change caused a fall in demand for many middle and lower-skilled jobs.

This combined with an erosion of trade union power and labour market deregulation led to a relative decline in wages at the lower end of the market.

At the same time, financial deregulation and a reduction in top rates of income tax contributed to a rise in salaries at the upper end.

The 1980s also brought a significant rolling back of the progressivity of the welfare state, including less generous out-of-work benefits and pensions and a less progressive income tax policy.

Result: the decade ended with a rising gap between the rich and the poor.

Change has been less dramatic since the 1980s - but with fascinating and nuanced undercurrents.

Wage inequality in the 1990s and 2000s grew relatively slowly (and was mitigated by the introduction of the minimum wage in 1997).

More generous state pensions, benefits for families with children, and the introduction of tax credits to supplement the incomes of the low-paid have all helped to stem any increase in overall income inequality. In fact, since the late 1990s, households in the bottom third of the income distribution have seen their incomes increase somewhat more rapidly than households in the top third of the distribution, on average.

However, the picture becomes more nuanced the more we look into the detail.  Since the late 1990s, the very poorest five per cent of households have become even poorer, partly as a result of stricter rules around benefit eligibility.

At the same time, the richest one or two per cent of individuals have seen their incomes grow far more rapidly than any other group, largely driven by pay increases in the financial and business services sectors.
Our most recent population-wide data runs until early 2013.

But it seems almost certain that inequality will have increased since then. The recession and its aftermath saw a large increase in the proportion of insecure work - part time work, temporary work, and out-sourced agency self-employment.

These trends have increased wage inequality, and are only just beginning to reverse.  

Changes to fiscal policy are also likely to have increased inequality. Many working-age benefits have been cut in real terms, reducing the incomes of the poorest households.

And although rises in personal allowances have taken some people out of income tax altogether, they have also provided a tax cut for all individuals earning above the personal allowance.

In terms of monetary policy, one of the side effects of the quantitative easing policy - or QE - pursued by the Bank of England is that it raises the prices of assets, including housing, pensions and other financial assets.

These types of assets are not evenly distributed, but heavily skewed, with the top five per cent of households holding 40 per of the assets. The QE policy is thus likely to have raised levels of wealth inequality.