Perhaps a Markov switching model or a threshold autoregressive model?
I have attached a graph representing data collected on a quarterly basis from 1995-2008. The x-axis represents the time - quarterly data.
Would an additive or multiplicative time series model be appropriate?
Or is it possible for me to use a simple smoothing exponential or double smoothing exponential to do forecasting?
Any suggestion would be appreciated.
Thank you very much