He, however, said the impact of the sudden withdrawal of 86 per cent of currency is "pretty much over" as the newly- printed 500 and 2,000 rupee notes hit the banking system, replacing the old 500 and 1,000 rupee notes that were voided overnight on November 8, last year.
India is estimated to have clocked a surprising 7.1 per cent GDP growth in 2016-17 fiscal with a 7 per cent growth rate in the October-December quarter, notwithstanding demonetisation.
Subramanian, who is here to attend the annual Spring Meetings of the International Monetary Fund and the World Bank, said the actual impact of demonetisation is not reflected in the GDP numbers.
"That being said, I do think that the headline number might not give the actual impact of demonetisation. I think we will get to know over the course of the next few months what the actual impact is going to be," he said.
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"A lot of impact of demonetisation is really a case of too early to tell and (we) will find out over the course of (the) next few months, except for the impact on the informal sector, which I do not think we are really going to get a handle on at all," he said.
Subramanian said that the popular response to this policy of Prime Minister Narendra Modi has "humbled him" in his understanding of Indian politics and to some extent economics as well.
Responding to a series of questions on demonetisation, the chief economic adviser said that it was over and it signalled a regime change.
Demonetisation on the part of the government does signal a "regime shift" which says "if you are not going to be compliant on your tax payments, the government is going to make extra efforts to do so", he said.
So, it is kind of signalling a regime change, he added.
He conceded that this was a step towards digitisation and broadening of the tax base.
"It is really about creating an infrastructure, using technology to better deliver government services in the long run," he said.