Introduced on day 23
Damped trend
A trend component whose contribution flattens as the horizon grows, governed by a damping parameter between 0 and 1; long-run forecasts converge to a constant.
In detail
With damping parameter phi below 1 each further step adds a smaller share of the last estimated slope, so forecasts level off instead of rising or falling without limit. Practical values are usually between 0.8 and 0.98; values near 1 are hard to tell apart from an undamped trend. It often forecasts long horizons better than a straight line because growth rarely continues unchanged.