Illustration: Jim Pavlidis. It shows that the share of total income going to the top 1 per cent of Australians has nearly doubled since the early 1980s, rising to 8.3 per cent on the latest count – the highest since the 1950s. So, on this measure, Bill Shorten is right to say that inequality is at about a 70-year high. But there are many ways to measure inequality, of which the top 1 per cent income share is just one. The most comprehensive survey of how income and wealth are distributed in Australia is provided by the Bureau of Statistics' Household Income and Wealth survey. For income, it measures the distribution of disposable income (i.e. after allowing for income tax paid and welfare benefits received) between households, using an "equivalence scale" to allow for the differing size and composition of households.

Bill Shorten says he will introduce a 30 per cent tax rate on discretionary trust distributions to people over the age of 18 if he wins power. Credit:Tracey Nearmy Clearly it matters quite lot for the living standards of a household with an income of $100,000 a year if that income is spread across a family of six, or just one adult. The bureau adjusts for this to get a measure of "equivalised disposable household income". The bureau conducts its survey every two years. The latest figures we have are for 2013-14. They show that the average equivalised household disposable income in 2013-14 was $998 a week. The median was somewhat lower – $844 – thanks to the asymmetric shape of the distribution, that is, the relatively small number of households who have relatively high incomes, and the relatively large number of households who have relatively low incomes. The bureau's data allows us to consider the distribution of income and wealth between "quintiles". That is, if you ranked all households from lowest to highest, and then divided the population into five equal-sized groups.

Let's start with income. After taking account of the number and age of people in the household, households in the highest-income quintile in Australia received over 40 per cent of total income in 2013-14. By comparison, households in the lowest quintile received 7.3 per cent of total income. This pattern has remained relatively stable over the past 20 years. While the average household income is now close to $1000 a week, the average for the lowest quintile is just $375, and $2037 for the highest quintile. Since 1994-95, the average household disposable income has grown by 67 per cent in real terms. But, while income in the lowest quintile grew by 58 per cent, income in the highest quintile grew by 80 per cent. So the poor didn't get poorer, but the rich got richer a lot faster than the poor got richer, thus widening the gap between rich and poor and increasing inequality. But the bureau also measures the distribution of wealth, which is even more unequally distributed than income – as it is in most countries. Income, of course, is a flow. Wealth is a stock. For its measure of wealth, the bureau uses a measure of "net worth", being the sum of a household's assets (property, shares, superannuation) minus its liabilities (home loans and other debts).

In 2013-14 the average household had assets of $954,800 and liabilities of $144,900, giving an estimated average net worth of $809,900. When ranked by their level of wealth, the top 20 per cent of Australians owned 62 per cent of total household wealth in 2013-2014. By comparison, the bottom 20 per cent of households owned less than 1 per cent of all household wealth. Housing makes up 60 per cent of all assets owned by Australian households (split between owner-occupied housing at 43 per cent and investment property at 15 per cent), and superannuation makes up a further 15 per cent. Although declining rates of home ownership are deepening wealth inequality, Australians' growing superannuation nest eggs have helped to limit the increase in wealth inequality overall. Of course, different types of households have fared differently. Lone person households of prime working age fared particularly badly over the decade and a half to 2009-10.

This is due in large part to less generous increases to the Newstart Allowance relative to the age pension (Newstart is indexed to consumer prices, and pensions to the more generous measure of wages). Households in the 55 to 65 age bracket have fared the best. They are more likely to be working than previous generations, while also drawing an income from investment housing (rent) and dividends from share ownership. Another important indicator of inequality is a "Gini coefficient". Gini coefficients range from 0 (perfect equality – everyone has the same) to 1 (perfect inequality – one person has all the income or wealth). It is possible to construct Gini coefficients for the distributions of both incomes and wealth. The bureau's figures reveal that Australia's Gini coefficient for income has risen from 0.302 in 1994-95 to 0.333 in 2013-14.

The Gini coefficient for wealth in 2013-14 was 0.605 – almost double the inequality of incomes. Inequality, on the Gini income measure, did not increase greatly from 1994-95 to 2003-04, as the Howard government's significant increases in the family tax benefit offset the effect of greater dispersion in market incomes. Between 2003-04 and 2007-08, however, income inequality worsened by almost 10 per cent, from 0.306 to 0.336, due to continuing dispersion in market incomes, plus a series of annual tax cuts favouring higher income earners. Between 2007-08 and 2011-12, in the aftermath of the Global Financial Crisis, the income Gini fell by about 5 per cent to 0.320. Unfortunately, this decline in inequality was almost entirely reversed in the latest survey for 2013-14, coming in again at 0.333. Overall, Scott Morrison is fairly correct to say that inequality of incomes has not changed dramatically since the GFC. Loading

But that's a pretty short time horizon, and the trend of the past decades is towards rising inequality. It's worth talking about.