"from the annual report, passenger trips have increased 11% from 2002 - 389.7m to 434.9m. However, car kilometres operated dropped from 81.4m to 77.1m. SMRTC has been aggressively cutting costs by cramming as much as people into each train and reducing frequencies since 2004, to maximise shareholder value."
One Less Car has screenshots of the relevant tables with that data.
If the analysis is correct, then the formula seems to be:
More passengers + less frequency = more money to be made = pissed off passengers (who will be ignored).
The photo above shows passengers unable to squeeze into the packed train, on a SUNDAY afternoon, supposedly Off-peak. I only managed to get into the third train, after waiting 6 minutes between trains. All because I wanted to get to City Hall from Dhoby Ghaut. One miserable station.