The Turnbull Government’s second Budget plots a course for spending that extends as far as 2021.

By then - assuming Malcolm Turnbull can win another election - he would have been Prime Minister longer than Paul Keating, and within sight of Malcolm Fraser’s 2671-day stay in the Lodge.

Projected spending levels included in Budget 2017 give at least some indication of his priorities as Prime Minister. By 2021 the prime minister is projected to have developed a legacy of increased social security spending fuelled by the growing cost of the National Disability Insurance Scheme (NDIS), alongside larger grants to the states and a greater public debt burden.

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Richard Holden, Professor of Economics at the University of New South Wales Business School, said the public today expects the government to pay for more services, with the NDIS being a prime example.

"There's bipartisan support for (the NDIS) and I think it's fair to say the overwhelming majority of Australians are in support of it - it just costs money," he said.

"(Forty years ago) the burden might have fallen on church or other community groups, or family and friends in a more direct way."

Malcolm Turnbull's legacy may be defined more by the political climate than any policy vision, according to John Hewson, former leader of the Liberal Party and now Chair of the Tax and Transfer Policy Institute at the Australian National University's Crawford School of Public Policy.

Mr Hewson said recent governments have struggled to implement fiscal strategy given politics has become increasingly populist and opportunistic.

"Governments have responded by becoming increasingly short-term," he said. "They are not working to a liveable medium-term strategy."

Treasurer Scott Morrison delivers Budget 2017

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Professor Holden said the Budget was one for the times, and suggests the prime minister's legacy will be adapted for those times.

"Certainly it looks like his legacy is not going to be the 'Abbott/Hockey 2014 Budget legacy', or the sort of legacy you might take from someone who was going to implement the recommendations of the National Commission of Audit," he said.

Historical records collected by SBS World News from the Budget archive highlight changing priorities in government over the past four decades.

For each Budget, the government of the day allocated spending into 13 categories, including defence, health, education and smaller categories such as recreation and culture.

The information identifies the cuts and investments made by Australia's prime ministers in the past four decades relative to the size of the economy.

It also highlights significant spending decisions, such as those adopted by Gough Whitlam and Kevin Rudd governments in education.

In 1974 federal funding was extended to government schools, and a schools stimulus package was rolled out in 2009 as a response to the Global Financial Crisis. Both are identified by spikes in this chart:

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Spending by function does not tell the whole story of the government’s policy platform. For example, some policies are not achieved by direct expenditure.

A $600 million component of the housing affordability package in this year’s Budget can be found on the revenue side of the budget, where capital gains concessions for foreign investors were scrapped.

This leaves government expenditure on housing and community amenities projected to hover around 0.2 per cent of gross domestic product for the foreseeable future - its lowest level in since Whitlam was Prime Minister.

The Budget papers justify the decrease in spending in housing and community amenities by saying it reflects the scheduled completion of payments made to the states under partnership agreements and completion of urban and regional development projects.

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Welfare and social security represents the largest share of expenditure in the Budget - more than one-third of all spending.

As part of supposed welfare reform in the Budget, the government revealed plans to increase activity tests for people on Newstart and run a trial into drug testing welfare recipients.

"These are populist initiatives, they’re not about genuine reform, they’re not really about budget repair,” Mr Hewson said, noting the government overlooked cuts to the largest components of the welfare budget - assistance to the aged, families and the disabled.

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"The debate about genuine reform of public spending is not there, and it’s easy to tap money from foreign aid and put it into police and whatever,” he said.

The Budget papers link an increase in spending on social security to the impact of the transition to the full NDIS.

The breakdown of the Budget by government ‘function' is a traditional component of the Budget papers, but also reflects a mentality of siloing government responsibilities.

Mr Hewson suggests this approach may not be in the nation’s best interests.

"We build these (portfolios) as fiefdoms or silos, but you need a wholistic approach,” he said.

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“In the context of health and ageing, you’ve got to do it in the context of the health budget, the ageing budget, the superannuation budget - it’s broader than the individual departments."

Mr Hewson - who was an adviser to two treasurers in the Fraser Government - said the tradition of the government cutting unnecessary expenditure by going through the Budget “line-by-line” extended back at least four decades.

Although an efficiency dividend has been applied to defence in this week's Budget, Mr Hewson said it was one area that had historically avoided cuts.

"They’ve poured money into defence and defence is a fiefdom unto itself, it’s never been subjected to the same budget scrutiny as other government departments,” he said.

The government has aimed to increase expenditure on defence to two per cent of GDP.

Annual defence spending is expected to grow by almost $4 billion over the next four years.

Together with an increase of capital investment, the defence budget is scheduled to meet the two per cent target in 2020.

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While useful for assessing the priorities of the Commonwealth, this picture of spending becomes more complicated in areas jointly delivered by state and federal governments like education, housing and health. The national government provides money to states to deliver local services, mostly through the collection and distribution of the Goods and Services Tax (GST).

These payments - the largest component of the “other purposes” category - have declined since the 1980s.

But they are on the way up again. Apart from GST payments, public interest debt is also included in this group, contributing to the rise predicted under Prime Minister Turnbull.

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