I am examining how investor sentiment affects the probability of stock market crises. I am using methodology similar to this paper https://ideas.repec.org/p/dij/wpfarg/1110304.html.
VIX (equivalents) data for a Canada, China and Australia is either not available or only available from 2008 (I need data for 2001-2015). However, V-Lab provides predictions for various GARCH models for the stock indexes that I am interested in, for example: http://vlab.stern.nyu.edu/analysis/VOL.AS51%3AIND-R.GARCH
I haven't studied GARCH models and have only a basic understanding of their uses. My question is, can historical GARCH predictions be used as a measure of stock price volatility (instead of VIX)? And are they used for academic research in this way?
If not, what other measures are commonly used to proxy the volatility of a stock Index?