TO share my experience: I have been working in civil service for 8 years. Local grad, from NUS, BBA with merit. 31 years old this year. Salary progression with the years as such:

2003: 2700
2004: 2900
2005: 3100
2006: 3300
2007: 4200
2008: 4500
2009: 4800
2010: 5300
2011: ...... still waiting for Jul MI... heh.

The annual increment is increasingly dependent on performance / appraisal. While there is indeed a 'benchmark' increment figure for your particular grade / rank, bosses can tweak these figures up or down by as much as 25%.

Salary package is also increasingly variable through the payment of variable bonuses. AN earlier thread mentioned that an average civil servant annual package is as much as 16 months. This is true. Depending on which service you are in, and your grade / rank seniority, this can vary widely. Much of these variable payments also dependant on economic conditions.

For my case, 2010 a bumper year. Coupled with a favourable assessment, my salary package in 2010 amounted to about 20 months :/