Revisions to official economic statistics are a fact of life. They happen all of the time. Many data are released on a "provisional" basis, and subsequently revised. Sometimes these revisions are quite minor, but there are also times when they can be downright embarrassing.
Periodiclly, national data agencies find the need to make extensive revisions, stretching back for a considerable period, to key economic data. If you're involved in the running of a major econometric model - perhaps for a central bank, or the like - then this poses some big problems.
I was in this situation for a spell, in an earlier life in New Zealand. I recall one occasion in the early 1970's when current account data was revised, and the leaders of the day had to stop gloating when a healthy surplus was revised to become a current account deficit. There was some serious fall-out.
So, it was with some interest that I read yesterday of the latest re-writing of the economic facts in New Zealand. For perfectly good reasons, Statistics New Zealand has revised its quarterly national accounts data back to March 2007. Some of the revisions are quite sizeable.
This is going to be something of a challenge for the modellers!
© 2012, David E. Giles