From a giant rubber duck to this year's cardboard city, size mattered during Lieven Bertels' four years as Sydney Festival director.

Yet the festival's revenue has shrunk by almost $4 million during his reign, with corporate sponsors and government cutting financial support for the annual arts event.

Under Bertels' predecessor Lindy Hume, the Sydney Festival Limited reported revenue of $25.6 million in the 2011-12 financial year. Three years later, the festival's 2014-15 revenue had fallen to $21.9 million.

The financial results for the 2015 festival were released last week to the Australian Charities and Not-for-profits Commission. Figures for this year's festival will not be reported until December 2016.

The 2015 festival received $5.6 million in government grants, more than $1 million less than the $6.8 million given to Hume's final festival in 2012.

However, the bulk of the festival's falling revenue was due to a sharp decline in sponsorship from $11.3 million in 2012 to $8.7 million in 2015.

This is despite the festival's website claiming "our corporate partners find Sydney Festival to be a comprehensive business solution …"

The festival's major corporate sponsors this year were The Star casino, Meriton and China Southern Airlines, while it no longer receives corporate backing from Zip Industries, Channel Nine and ANZ Bank.

The festival spent twice as much on fundraising in 2015 compared to the previous year, yet raised less money. In 2015, $142,184 was spent to raise $434,314, while in 2014, the festival's fundraising activities only cost $72,019 yet generated more than half a million dollars.

The 2015 festival earned $5.1 million at the box office, a dramatic improvement from the $4.2 million box office of Bertels' first festival in 2013.

In contrast, Hume's final festival in 2012, which featured the free Festival First Night program, Black capital and Australian play The Boys, recorded $4.9 million at the box office.

Despite shrinking revenue, the festival reported a profit of $684,831 in 2015 compared to a $28,339 loss in 2014. This could be due to the festival spending $700,000 less on shows in 2015, compared to the previous year.

The festival's overall financial position has also dramatically improved since 2010 when it reported a loss of $2.49 million.

The company that runs the Sydney Festival is a not-for-profit organisation with a constitution that states it must not be operated for the purpose of profit.

The Sydney Festival executive director Christopher Tooher​ was unavailable to comment and the festival declined to provide any explanation of its finances.

But Bertels' tenure at the festival has coincided with cuts in funding from the NSW government that led to the end of the popular Festival First Night.

"You can't live in a bubble in the arts – that's not to say you won't fight hard to get every dollar available to the arts and make the case it's money well spent," he said last year.

The festival's annual reports suggest it is spending less money on shows and free events, while administration costs have remained about the same.

The 2015 festival's program cost $10.5 million – just under half of the total expenses of $21.2 million – compared to $11.2 million spent on the previous year's program.

Administration expenses were $5.3 million in 2015, while marketing and publicity consumed another $1.4 million.

In contrast, the 2012 festival program cost $12.5 million, while $5.4 million was spent on administration and $1.7 million on marketing and publicity.

The 2015 festival also spent less of its programming budget on free events, with 26 per cent of its budget going on the free program compared with 37 per cent in 2013.

Free events attracted more than 430,000 visitors in 2013, dropping to almost 400,000 at last year's festival.