Put simply, says Mr Joshi, this level of information can predict the vote - "and these predictions usually never go wrong".
In India, the problem is compounded because it's "a data society that was planned and built by the government without any safeguards", Mr Kodali says.
Getty Images India has built the world's largest biometric ID database - the Aadhaar schemeMeanwhile, a data protection law passed by the government last year is yet to be implemented, experts say.
As Mr Joshi puts it, India entered the election year as "the biggest possible data mine in the world right now".
The thing is, no one is doing anything illegal, says Mr Joshi. "

India election: Fighting for votes in 'the world's biggest data mine'