Pronab Sen, India's chief statistician and secretary, MOSPI, spoke to Pragya Singh. Excerpts:Why is the new index taking so long and why are inflation numbers always revised?How reliable is the advanced estimate?An IMF report has said inflation is lower than we think if we adjust seasonal variations. What do you make of it?Is inflation headed up or down?What can your ministry do to ensure that data collection is more efficient and reliable?Would it be better if data were released only every month instead of every week?