These are replication files for Dueker(1997), "Markov Switching in GARCH Processes and Mean-Reverting Stock-Market Volatility," J of Business & Economic Statistics, vol. 15, no 1, 26-34 using a reconstruction of the original data file. Dueker fits several different models with different types of switching. All of models allow the mean to switch, but two of these have "variances" switching, and two have the degrees of freedom in the conditional t density switching in different ways.
Switching GARCH (as opposed to ARCH) models require "collapsing" the history of the regimes in some fashion. Dueker waits one period longer for this than Gray(1996) does in "Modeling the conditional distribution of interest rates as a regime-switching process", J. of Financial Economics, vol 42, pp 27-62. This actually makes it easier to adapt the technique to different models than Gray's.
Switching GARCH models is one of the topics in the course materials: viewtopic.php?f=24&t=1185
