I conducted Stochastic Frontier Analysis (SFA) using the command 'frontier' with the natural log of my output and inputs, followed by the command 'predict te.' My technical efficiency values are between -2.79 and 2.79. My understanding was that the higher the value the more efficient, and the lower the value the least efficient. However, I've been told that SFA scores are only to be bound between 0 and 1. So, I'm curious if anyone has any insight into my values? Thank you!