Hello everyone. I am experiencing some issue with tfdea (technology forecasting using Dea), and I would be grateful to anyone willing to help.
I am using tfdea on a dataset containing information on fighters (first flight date, max speed, climb ratio, range, engine's power-to-weight ratio).
My dmu is the fighter model; my year is the first flight year. Following the literature, I am specifying an output-oriented model, with variable returns to scale and constant inputs (=1 for every dmu). The outputs are max speed, climb ratio, range, engine's power-to-weight ratio.
Being an output-oriented model, I would expect theta_tk coefficients to be >=1 (=1 for the efficient dmu, >1 for inefficient dmu).
However, for two dmu in my dataset I get theta_tk=0.
How do I interpret that?
I looked at the features of those two specific fighters, and I couldn't notice anything strange or particular.
I get "normal" results (with theta_k>=1) if I don't include the engine's specific power in the model.
I am not posting specific commands or examples because everything seems to work fine; I'm just unable to interpret these results. However, if you need more info, I will provide them.
Thanks to anyone who might be able and willing to help.
I am using tfdea on a dataset containing information on fighters (first flight date, max speed, climb ratio, range, engine's power-to-weight ratio).
My dmu is the fighter model; my year is the first flight year. Following the literature, I am specifying an output-oriented model, with variable returns to scale and constant inputs (=1 for every dmu). The outputs are max speed, climb ratio, range, engine's power-to-weight ratio.
Being an output-oriented model, I would expect theta_tk coefficients to be >=1 (=1 for the efficient dmu, >1 for inefficient dmu).
However, for two dmu in my dataset I get theta_tk=0.
How do I interpret that?
I looked at the features of those two specific fighters, and I couldn't notice anything strange or particular.
I get "normal" results (with theta_k>=1) if I don't include the engine's specific power in the model.
I am not posting specific commands or examples because everything seems to work fine; I'm just unable to interpret these results. However, if you need more info, I will provide them.
Thanks to anyone who might be able and willing to help.
