George Kapetanios, Simon Price and Sophie Stone.
Structural breaks are a major source of forecast errors, and few come larger than the recent financial crisis and subsequent recession. After a break, formerly good models stop working. One way to cope is to discount the past in a data driven way. We try that, and find that shortly after the crash it was best to ignore almost all data older than three years – but now it is again time to take a longer view.