I have a very simply question about Unobserved Components Model.
I have a data set of 63 years. The data is declining for the entire time period but the slope is stochastic. The parameter of my slope term is negative but the level is positive [in the Trend Information (Based on the Final State) table]. I can interpret the slope but should the level not be negative if the data is decreasing?
I use the command
proc ucm data = lan;
id year interval = year;
model Eco ;
irregular ;
level variance=0 noest;
slope ;
run ;