## 2 Background
As we will detail, these centrality scores will be incorporated into a DEA process as input variables. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Article** & **Method** & **Units** & **Inputs** & **Outputs** \\ \hline [PERSON] et al. [4] & DEA-BCC and TFP index & 14 US airlines & \multicolumn{2}{c}{Number of cores} & Available seat-kilometers \\ \cline{3-5}  & & & Employees & Passenger service \\ \cline{3-5}  & & & Fleet & Revenue \\ \hline [PERSON] [29] & DEA-CCR and two-stage & \multicolumn{2}{c}{} & Labor & \\ \cline{3-5}  & & & Fuel & Seat-miles \\  & & & Fleet-wide passenger seating & \\  & & & capacity & \\ \hline Barros and Peypoch [35] & DEA-CCR and two-stage & \multicolumn{2}{c}{} & European airlines & \multicolumn{2}{c}{Employees} & Revenue per passenger km \\ \cline{3-5}  & & & Operational cost & EBIT \\ \cline{3-5}  & & & & Planes & (Euros million) \\ \hline Merkert and Hensher [19] & Standard DEA and & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} \\ \cline{3-5}  & & & airlines & & \\ \cline{3-5}  & & & Full-time equivalent workers & Revenue tome kilometers \\ \hline Arjomandi and & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} \\ \cline{3-5}  & & & Number of full-time & \multicolumn{2}{c}{} \\ \cline{3-5}  & & & equivalent employees & (TKA) \\ \hline \multirow{3}{*}{\begin{tabular}{c} \end{tabular} } & \multirow{3}{*}{Bootstrapped DEA} & \multirow{3}{*}{48 international} & \multicolumn{2}{c}{Number of full-time} & \multicolumn{2}{c}{} \\ \cline{3-5}  & & & airlines & equivalent employees & (TKA) \\ \cline{3-5}  & & & Total number of flying hours & \multicolumn{2}{c}{} \\ \cline{3-5}  & & & divided by average daily & \multicolumn{2}{c}{} \\ \cline{3-5}  & & & revenue hours & \\ \hline [PERSON] et al. [32] & Slacks-based measure (SBM), & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} \\ \cline{3-5}  & & & & \\ \cline{3-5}  & & & & \\ \hline \multirow{3}{*}{\begin{tabular}{c} Lee and \\ Worthington [36] \\ \end{tabular} } & \multirow{3}{*}{\begin{tabular}{c} Boosttrapped DEA and \\ bootstrapped \\ \end{tabular} } & \multirow{3}{*}{\begin{tabular}{c} 42 US and \\ European airlines \\ \end{tabular} } & \multicolumn{2}{c}{} & The average number of & \multicolumn{2}{c}{} \\ \cline{3-5}  & & & employees & \multicolumn{2}{c}{} \\ \cline{3-5}  & & & Total assets in US dollars & \multicolumn{2}{c}{} \\ \cline{3-5}  & & & & Kilometers flown & \\ \hline Jain and Natarajan [46] & Variable returns to scale & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} \\ \cline{3-5}  & & & & \\ \cline{3-5}  & & & & \\ \cline{3-5}  & & & & \\ \hline \multirow{3}{*}{[PERSON] and Li [28]} & \multirow{3}{*}{Virtual frontier} & \multirow{3}{*}{\
\begin{tabular}{c} 11 airlines from \\ Asia, America, \\ Europe, and \\ Oceania \\ \end{tabular} } & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} \\ \cline{3-5}  & & & & \\ \cline{3-5}  & & & & \\ \cline{3-5}  & & & & \\ \cline{3-5}  & & & & \\ \cline{3-5}  & & & & \\ \cline{3-5}  & & & & \\ \cline{3-5}  & & & & \\ \cline{3-5}  & & & & \\ \cline{3-5}  & & & & \\ \cline{3-5}  & & & & \\ \cline{3-5}  & & & & \\ \hline \multirow{3}{*}{
\begin{tabular}{c} [PERSON] et al. [33] \\ \end{tabular} } & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} & \multicolumn{2}{c}{} \\ \cline{3-5}  & & & & & \\ \cline{3-5}  & & & & & \\ \cline{3-5}  & & & & \\ \cline{3-5}  & & & & \\ \cline{3-5}  & & & & \\ \cline{3-5}  & & & & \\ \cline{3-5}  & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Summary of literature related to DEA (data envelopment analysis) in the airline industry. BCC: Banker–Charnes–Cooper. CCR: [PERSON]–Cooper–Rhodes. EBIT: Earnings before interest and tax.