Results of impacts( ) for partitioned impact measures
Hi all -
I am creating partitioned impact measure estimates using impacts( ) with the argument `Q' set to the desired number of orders of neighbourhood, say, Q = 5. The model is a Spatial Durbin model and the code is fairly standard:
I have read that the results for direct impacts of order 1 (immediate neighbours) should be 0 and, similarly, that for indirect impacts of order 0 (local area) should also be 0. I have certainly seen some examples that reflect this, and as I understand things, the logic makes sense.
However, not only do my results not have zeros in these slots, but as I search for confirmation online I also see other examples that don't. Mine look more like this:
Q2 0.003234086 <== Should be 0?
Q1 0.02869280 <== Should be 0?
I am assuming that the expectation of zeros as indicated is correct and that my results are flawed. However, I have yet to locate a problem and the fact that I see other examples with non-zero entries in these slots has left me confused.
My question is: Is there ever a situation in which it is reasonable to expect non-zero entries in these order-of-neighborhood slots as indicated above? If there is, how might these non-zero entries be explained given that for indirect impacts it seems reasonable to expect no effects from the local area, for example?
I'm sensing something obvious here (apologies in advance) - perhaps lock-down is getting me frazzled. Any help appreciated. In the meantime, I'll maintain my assumption that the results are wrong and keep re-checking everything that has led me here.