Non-parametric evaluation of returns to scale of production units in standard DEA models becomes problematic when their underlying technologies involve negative data. The methodology recently offered by Allahyar and Rostamy-Malkhalifeh (2015) (hence after called ARM model) is of some help to...

Congestion is an economic phenomenon of overinvestment that occurs when excessive inputs decrease the maximally possible outputs. Although decision-makers are unlikely to decrease outputs by increasing inputs, congestion is widespread in reality. Identifying and measuring congestion can help...