This week's federal budget was not an end to the hard limits on average staffing level numbers, as perhaps was initially assumed, but an evolution.

Finance Minister Simon Birmingham's admission that sometimes it might be more "efficient and effective to use ongoing staff" is only a shift in degrees, not a capitulation or even a retreat.

This mirrors other public administration constraints such as the efficiency dividend, which continue to serve a purpose, but history has shown become counterproductive when abused.

The previous Rudd-Gillard government was never going to solve the nation's structural budget problems by jacking the rate of public agency trimming - all it did was gut decades of knowledge from the centre of policymaking.

Tight controls on the size of the public service have served the last three prime ministers in Coalition governments in several ways.

Firstly, the approach was used very effectively under Tony Abbott's government to show something that looked meaningful as his ministers were spuriking their Smaller Government Agenda.

Holding (mostly) steady on the overall size of the APS helped Malcolm Turnbull calm the horses in his caucus as he attempted significant reform in how government did business and adopt digital transformation.

While for Scott Morrison, micromanaging the public service's size is another way of reminding them that as mere functionaries, they not there to create policy, but implement it.

None of those reasons had any relationship to the growth in the size of Australian population or where in the economic cycle we were.

"Fifteen years downstream from the 2006-07 benchmark, the range and scope of services provided by the government has grown with the nation," Senator Birmingham wrote in his preface to agency resourcing budget paper.

Australia's population has grown nearly a quarter in over that time period, so in real terms we have a much poorer and thinner public service, while every survey of public servants say the challenges are now even greater.

Public good is difficult to measure, while staffing levels and administration costs fit nicely on a ledger.

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