It appears that the bench making such drastic decisions have little knowledge of human psyche. Smaller increments from time to time would not attract so much attention and ire of the consumer community as a jump of 5% in one go. Germany started with a GST of 2% and after two decades they are around 20% or more. One hears a similar story about Singapore.
The Law of Economics and the Law of Human Psyche are different ball games. Trying to fill State coffers in a short period of time cannot help lift sagging economies. It's generally on the contrary, and does not earn public support but only their wrath. more