The State's estimated liability for funding public service pensions has fallen from €116bn in 2009 to €98bn today.
The decrease is due to the fall in public service staff numbers by around 30,000 and the pay cuts implemented since 2008.
Sources said the 2009 estimate of €116bn had assumed that staff numbers would have increased and that pensions would be linked to original salaries prior to the pay cuts.
They also noted that the Haddington Road Agreement will prevent any pay increases before 2016.
Had recruitment and pay not been reduced since 2008, the sources said the pension liability could have reached €130bn.