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hi
I want to estimate a GARCH(1,1)model but I want the sum of parameters in GARCH equation to be less than 1 to ensure stationarity. can you help please and tell me how can I put this restrictions in the model?
I really apperciate your help[/b]

You may not need to put such a constraint in advance. Just estimate your model without imposing any restrictions, and see if the results violate that condition. You should check the following link to learn how to put limits on estimated coefficients: http://forums.eviews.com/viewtopic.php? ... ction#p103 Please note that, you may need to set up a logl object to estimate a more flexible GARCH model. And fortunately, there have been plenty of discussions in the forum on this issue as well.