Couples with children in the poorest fifth of households will lose $1146, or 2.7 per cent of average incomes, should all budget measures be successfully introduced. Prime Minister Malcolm Turnbull, on the campaign trail in Penrith with one-year-old Freya Brown, said last week "the budget is very fair". Credit:Andrew Meares By contrast, relatively well-off couples with children in the second-top income quintile will be $392 a year better off by 2018-19, modelling of the budget's impact by ANU's Centre for Social Research and Methods found. "The analysis … clearly shows that the proposed measures in the 2016-17 budget would impact low income families with children more significantly than other families," the report says. "The losses for the middle and top income groups are proportionately much less than low income families." It concluded the budget will have a "regressive impact".

The modelling comes days after part-time truck driver Duncan Storrar sparked political furore over budget fairness when he asked Assistant Treasurer Kelly O'Dwyer on ABC TV's Q&A why low-income earners like him missed out on tax relief. Prime Minister Malcolm Turnbull has made fairness an "absolute objective" for government reforms and said last week "the budget is very fair". But the ANU modelling shows the least well-off 40 per cent of families "are the most heavily impacted" when everything in the budget is taken into account. The modelling also challenges Labor's claims to fairness because it supports a big hike in tobacco excise. Implementing a further four annual 12.5 per cent increases in tobacco excise from September 2017 will "more significantly impact low-income families", the report said. This policy was first proposed by Labor and was subsequently adopted by the government in last week's budget. The modelling puts a dollar figure on how different income groups will be affected in 2018-19 by all the provisions in last week's budget.

This includes some so called "zombie measures" left over from the Abbott government including cuts to family tax benefits and childcare reforms due to be implemented in the next term of government. The report's author, Dr Ben Phillips, said the modelling showed low-income families with children were shouldering "most of the responsibility" for budget repair. "It's not as extreme as the previous two budgets but, again, high-income groups are largely unaffected with the exception of a small number of high-wealth families impacted by the superannuation changes," he said. Superannuation changes in the budget that target high-income earners mean a typical family with children in the wealthiest fifth of households stands to lose $664 a year – 0.3 per cent of average incomes for that cohort. The report said the super changes helped provide a "more progressive budget impact" but this was offset by other measures.

"The superannuation changes, while significant, are not enough to alter the conclusion that this budget has a regressive impact," the report said. The modelling did not include the tax benefit that will go to high income earners after the 2 per cent deficit repair levy is withdrawn, as planned, in mid-2017. Modelling reveals how the mix of budget measures affects different household types Every budget is released amid a storm of spin. But now it doesn't take long for independent modelling to reveal the true impact on households. Analysis of the controversial 2014 budget by the National Centre for Economic Modelling revealed how the poorest 20 per cent of families would pay $1.1 billion more into government coffers than the richest households to help repair the budget.

Experienced modeller Ben Phillips was involved in Natsem's modelling of the 2014 and 2015 budgets and has now crunched the numbers on the 2016 budget for the Australian National University's Centre for Social Research and Methods. Dr Phillips says modelling plays an important role in helping people understand how complex budget changes will affect them. "Obviously, governments aren't always that keen to provide great detail about the impact of budgets because there are often losers," he said. "But modelling provides the cold hard facts." What did this modelling do?