New Delhi, Sept. 4 -- India has finally moved to a five-slab GST regime, after the reform promised by the Prime Minister from the ramparts of the Red Fort. The previous six-rate system has been recast: the top rate has risen from 28% to 40%, and the 12% rate has been eliminated. The new rates are nil, 5%, 18% and 40%, besides the 3% rate for gold.

One way to assess the impact of rate changes for the goods and services tax (GST) is to look at the celebration or criticism for the rate adjustment on specific items. Another way is to consider the effect on the economy as a whole.

Before doing that, let us welcome the resolution of numerous inverted duty complications and the standardisation of rates on synthetic and natural fibres. This spa...