Its 16-point contribution to lifting the combined gross domestic product of the world's largest economies detailed in a 25-page addendum to the G20 communique consists largely of previously announced measures, most of them election commitments or budget measures.

The measures include previously announced spending on road and rail projects, the six-month waiting period of Newstart for young jobseekers and the paid parental leave scheme. Next to each is an annotation describing it as "new".

A spokesman for  Treasurer Joe Hockey said any measure adopted since last year's G20 meeting in St Petersburg in Russia in  September is defined as new. The St Petersburg meeting was held on the eve of Australia's 2013 election, allowing the Coalition to claim that each of the initiatives is new for the purpose of making a commitment to boost global economic activity.

The 16 Australian measures have been assessed by officials from the International Monetary Fund and the Organisation for Economic Co-operation and Development, which  have made an estimate of how much they will boost economic activity.

That estimate has not been published, either for Australia or for any of the other G20 members. All that has been made public is the officials' estimate of the total contribution, which they say will amount to 2.1 per cent of the G20's combined GDP by 2018. The benchmarks that will be used to assess the success of the  measures are vague.

The benchmark for the success of Australia's paid parental leave scheme is said to include "the progress of legislation through the Parliament, the take-up of the scheme, retention rates and female labour force participation rates".

The progress of each nation on implementing its promises will be assessed each year by a panel of officials from international organisations.

Addressing concerns that it would be difficult to tell whether  the benchmarks had been met and whether  they had boosted economic growth as much as promised, Prime Minister Tony Abbott said 12 months ago people thought  this G20 would never come to any agreement.

"We have come to a series of very important agreements, so the next objection is to say, well, they will never actually implement them."

Many of the commitments made by other nations have also been previously announced. The US has committed itself to completing negotiations on the Trans-Pacific Partnership trade agreement. China says it will "speed up" talks on concluding a free trade agreement with Australia.

Peter Martin is economics editor of The Age.

Twitter: @1petermartin