Hi,

I am doing a study on firms' marketing efficiency. I calculate the efficiency using SFA function in the Frontier package in R. I then test a hypothesis where marketing efficiency is an independent variable. The results suggest that marketing efficiency is significant with a negative effect which is counter-intuitive.

I am not sure if the sfa function already gives me the reverse of the distance from the frontier (mu in the below model) when I use the function efficiency in R as efficiency or do I need to reverse it myself (efficiency = 1-mu)?

output= input1 + input2 + input3 + e-mu