Luka Neralic

William Wager Cooper was a great man as a scientist, professor, researcher and friend. He was always ready to help anyone from students to friends and colleagues.
I first met Professor William W. Cooper during my postdoctoral study in 1985/86 as a Fulbright Scholar with Professor Abraham Charnes in the Center for Cybernetic Studies at the University of Texas at Austin. In 1985 the first paper of Charnes, Cooper, Lewin, Morey and Rousseau on sensitivity and stability analysis in Data Envelopment Analysis (DEA) was published and I began working with Professor Charnes in that area. Professor Charnes and I obtained some new results which I shared with Professor Cooper, since he was one of founders and leading researchers in DEA. It was the beginning of our contacts which continued until recently. I remember our meeting at The 12th Triennial Conference on Operational Research, IFORS’90, June 1990 in Athens, Greece. Professors Charnes and Cooper were keynote speakers on DEA and I presented a joint paper with Professor Charnes entitled ”Sensitivity Analysis of the Proportionate Change of Inputs (or Outputs) in Data Envelopment Analysis”. In July of 1991 we met at The 11th European Congress on Operational Research EURO XI – in Aachen, Germany. I also met Professor Cooper at The 14th IFORS Conference in Vancouver, Canada – in July 1996. It was also an opportunity for me to meet Professor Cooper’s wonderful wife, Ruth. After a discussion with Professor Cooper at the Conference I sent him a draft of my paper on sensitivity analysis of the Additive model for the case of change of all data. I incorporated his constructive comments into my paper „Sensitivity in data envelopment analysis for arbitrary perturbations of data“, which was published in 1997 in Glasnik Matematicki. Professor Richard E. Wendell from The University of Pittsburgh and I worked in 1996 on a generalized additive, categorical model in DEA. Professor Wendell, as a very good friend of Professor Cooper, sent him our preliminary results asking for his opinion. Professor Cooper’s response was a ten-pages letter written by hand. In our paper published in 2000 is written: „The authors are indebted to Professor Cooper for his many insightful comments and suggestions.“ In July, 1997 Professor Cooper and I attended the EURO XV – INFORMS XXXIV Joint International Meeting – in Barcelona, Spain. Professor Cooper presented a very interesting paper „Scalar Measures of Inefficiency in DEA“. After my presentation of the paper ”Sensitivity in Data Envelopment Analysis for Arbitrary Perturbations of Data” we discussed the papers. At the Sixth European Workshop on Efficiency and Productivity Analysis, at Copenhagen, Denmark in October 1999, I was together with my former master student and Ph. D. student Valter Boljuncic, who is Professor at the University of Pula and a member of Croatian Parliament. Professor Boljuncic presented our joint paper ”Evaluation of Robustness of Decision Making Units Using Dual Multipliers”. At the Workshop’s banquet we were seated at the table with Professor Cooper and Professor Rajiv Banker and had a very nice long chat during dinner. Here I learned many interesting facts about Professor Cooper’s life including his professional boxing career and the situation with his doctorate. During his stay as a Fulbright Scholar at SUNY, Stony Brook, Professor Boljuncic visited Professor Cooper in the spring of 2001 at the University of Texas at Austin and gave a talk there. In February 2010 I sent Professor Cooper a joint paper with M. Asgharian and M. Khodabakshi on Congestion in Stochastic DEA asking for his opinion of it. His answer in April 2010 was: „Dear Luka: Thank you for giving me an opportunity to read your very interesting paper on Congestion in Stochastic Data Envelopment Analysis. Please also excuse this delayed response by my having been ill and out of the office for some time.“ After comments on the paper he wrote: „I hope you find these comments to be of some interest and many thanks for giving me the opportunity of renewing our contacts. Bill“. I used to send Christmas and New Year greetings to Professor Cooper. He always answered, like in 2008: „Dear Luka: Thanks for your good wishes. It was nice to hear from you, I hope this finds you well, happy and thriving. Best regards, Bill.“ William Wager Cooper was a great man as a scientist, professor, researcher and friend. He was always ready to help anyone from students to friends and colleagues. His ideas had a tremendous influence on the new areas of Management Science, Operations Research and Economics. Among a number of his fundamental contributions, he was a founder of Data Envelopment Analysis together with Abe Charnes and Eduardo Rhodes in their seminal paper published in 1978. I am very fortunate to have had the honor and pleasure to be among those who knew him. I am most grateful for his many kind and constructive comments on my research, and I will always cherish his memory!
Luka Neralic, Croatia August 2012