# Overall Equipment Effectiveness: Systematic Literature Review and Overview of Different Approaches
## 4 Discussion and Conclusions  
Companies use measurement systems to identify areas on which to focus to enhance performance and productivity. It is assumed that all parameters that can be measured, can be improved. Through this systematic study--and with the formulation and development of the proposed RQs--the state of the art, evolution, and future trends of OEE indicators were better understood.  
The OEE started as a component of TPM and was used to increase productivity and reduce time, speed and quality losses. [PERSON] et al. (2000) [29] reported that the indicator involves aspects other than monitoring and controlling because it provides performance data to make decisions by combining techniques, systematic method and process improvement. The practical and academic interest indicated over time was demonstrated in this study review and in the answer to the RQs. According to the answer to the first question, academic interest increased in the last five years and that the indicator is used beyond production maintenance. This study illustrates the evolution of keywords related to OEE beginning from terms relevant to maintenance and production to concepts related to six sigma, lean manufacturing, sustainability, etc. The second question resulted in a compilation of models developed based on OEE; the results presented a framework of areas or sectors where the indicator was applied. The models have evolved for the analysis of complete production lines, material handling, transportation, ports and sustainability. The answers to the final question were the principal contributions of some authors and future trends that are expected to be followed.  
In conclusion, the results indicated that OEE is an emerging topic that can be used as input information for decision-making in business. Industry 4.0, which is based on cyber-physical systems and information digitalization, facilitates the accumulation and transformation of real-time process information into decisions to reduce uncertainty in the results. After analyzing the approaches of the OEE indicator it can be noted that it is adaptable to different domains by measuring the effectiveness not only of production equipment but also the effectiveness of material, economic and human resources. This will require an in-depth study of the process to determine the losses, variables and factors to be included in other OEE approaches. Future studies regarding OEE can be transferred to the logistics sector and may be included in the formulation of environmental variables, such as carbon footprint generated during a specific process. In supply chains, OEE can be used to measure the productivity of cargo movement equipment in a warehouse. Meanwhile, in the service sector, OEE can be used to measure client satisfaction in terms of the availability, performance and quality of the services received. Additionally, an OEE-based model can be incorporated into a balanced scorecard to visualize the overall productivity of a business. All these measures provide a general perspective of the business and achieve the main objectives of production, i.e., increasing productivity and reducing waste.  
Conceptualization, M.P.L. and J.R.; methodology, M.E.H.K. and L.d.C.N.C.; software, M.E.H.K.; validation, L.d.C.N.C.; formal analysis, L.d.C.N.C.; investigation, L.d.C.N.C.; data curation, M.E.H.K. and L.d.C.N.C.; writing--original draft preparation, L.d.C.N.C.; writing--review and editing, M.P.L., J.R., M.E.H.K. and L.d.C.N.C.; supervision, M.P.L.; project administration, J.R. All authors have read and agreed to the published version of the manuscript. This research received no external funding.  
The authors would like to acknowledge the scholarship granted by the government of Panama under the IFARHU--SENACYT program for a candidate from 2018 to 2021.  
The authors declare no conflict of interest.