Abstract
Commercial cheating, that is, counterfeit products and lower quality products sold as genuine products, exists extensively in many countries of the world, especially in the developing countries. In this paper, we investigate the phenomena of commercial cheating, study the optimal cheating actions of inventory managers under a monitoring and limiting regime from the industrial administration office (IAO for short) and demonstrate the efficiency of monitoring and limiting such cheating activities. A newsvendor model has been considered for the inventory manager to order different quality products with different set-up costs. The model, a kind of extension of the general newsvendor problem, is viewed as a shocked inventory model. We analyse some properties of the optimal cheating policies from the point of view of an inventory manager, and investigate the effectiveness of both the punishment level and the checking rate.
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Acknowledgements
We thank the anonymous referees for their valuable comments that helped improve this paper. This paper was supported partially by the National Natural Science Foundation of China under Grants 60274050, 70221001 and 70328001.
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Appendix A
Appendix A
In this Appendix, we present, the proof of Proposition 2 and Theorems 1 and 2.
A.1. Proof of Proposition 2
Proof On the curve M2, . Taking the derivative of with respect to y1, we can obtain . That is
On the curve M1, , also we have
Then we can derive that
On the curve Γ2, G(y1, Ψ2(y1))=K2+G(y1, Y2(y1)), and then,
Now we obtain
Similarly, on the curve Γ1, we have G(Ψ1(y2), y2)= K1+G(Y1(y2), y2) and then
Simplifying the above equation, we have
The conclusion holds if and only if
The last inequality holds because
Now the proof of the proposition is complete.
A.2. Proof of Theorem 1
Proof Now we prove this theorem in four cases, X∈O1, X∈O2, X∈O12 and X∈Ō.
(1) For the case X∈O1, we increase X to Y′. Then, we measure three possible subcases:
Subcase (1.1): Assume that y1′>x1 and y2′>x2. When x2⩾S2, recall the definition of M1 and with the help of Proposition 1, we have K+G(Y′)⩾K+G(Y1(y2′), y2′)⩾ K+G(Y1(x2), x2)>K1+G(Y1(x2), x2). Otherwise, x2<s2, and we also have K+G(Y′)⩾K+G(S)=K1+G(S′)⩾ K1+G(Y1(x2), x2).
Subcase (1.2): Assume that y1′>x1 and y2′>x2. If x2⩾Ψ2(x1), recalling the definition of Ψ2, we have K2+G(Y′)⩾G(X)>K1+G(Y1(x2),x2). Otherwise, x2<Ψ2(x1). Then, let Ȳ=(x̄1, x2)∈Γ2, and we have
Subcase (1.3): Assume that y1′>x1 and y2′>x2. Obviously, we have K1+G(Y′)⩾K1+G(Y1(x2), x2).
Combining the three subcases, we always have G(X)⩾K+G(Y1(x2), x2), which means that to increase inventory X to (Y1(x2), x2) is optimal in this case.
(2) For the case X∈O2, the proof is similar to that of part (1).
(3) For the case X∈O12, we increase X to Y′. Then three subcases will be considered.
Subcase (3.1): Assume that y1′>x1 and y2′>x2. Obviously, we have K+G(Y′)⩾K+G(S).
Subcase (3.2): Assume that y1′>x1 and y2′>x2. Recalling the definition of Y1(·), we have K1+G(Y′)⩾K1+G(Y1(x2), x2)⩾K1+G(S′)=K+G(S).
Subcase (3.3): Assume that y1′>x1 and y2′>x2. By the definition of Y2(·), we have K2+G(Y)⩾K2+G(x1, Y2(x1))⩾ K2+G(S″)=K+G(S).
Combining the three subcases, and we always have G(X)>K+G(S), which means that increasing inventory X to S is an optimal selection in this case.
(4) For the case X∈Ō, we have four subcases.
Subcase (4.1): Assume that X⩾Γ1, X⩾Γ2, X⩾Γ and X<S. We increase inventory X to Y′. If y1′>x1 and y2′>x2, then we have K+G(Y′)⩾K+G(S)⩾G(X). If y1′>x1 and y2′>x2, then we have K1+G(Y′)⩾K1+G(Y1(x2), x2)⩾G(X). If y1′>x1 and y2′>x2, then we also have K2+G(Y′)⩾K2+G(x1, Y2(x1))⩾G(X). It means that doing nothing is an optimal selection.
Subcase (4.2): Assume that Γ1⩽X<M1 and x2⩾s2. We increase inventory X to Y′. When y1′>x1 and y2′>x2, we have K+G(Y′)⩾K+G(Y1(y2′) y2′)>K1+G(Y1(x2), x2)⩾ G(X). When y1′>x1 and y2′>x2, we have K1+G(Y′)⩾ K1+G(Y1(y2′) y2′)⩾K1+G(Y1(x2), x2)⩾G(X). When y1′> x1 and y2′>x2, and if X<M2, we have K2+G(Y′)⩾ K2+ G(x1, Y2(x1))⩾G(X); otherwise, X⩾M2, and we also have K2+G(Y′)⩾K2+G(X)>G(X). Now we show that doing nothing is an optimal selection.
Subcase (4.3): Assume that Γ2⩽X<M2 and x1⩾s1. We increase inventory X to Y′. Using a similar analysis, we can derive that doing nothing is an optimal selection.
Subcase (4.4): In the subcase of X⩾M1 and X⩾M2, we also can derive that doing nothing is optimal similarly.
So for the case 4, we know that doing nothing is optimal.
A.3. Proof of Theorem 2
Proof Now we prove this theorem in five cases, that is X∈O1, X∈O2, X∈O12, X∈O and X∈Ō.
(1) For the case X∈O1, when x2⩾s̄2, the proof is similar to that of part (1) in Theorem 1.
When x2<s̄2, we increase X to Y′ and consider three subcases.
Subcase (1.1): If y1′>x1 and y2′>x2, we have
Subcase (1.2): If y1′=x1 and y2′>x2, we obtain
Subcase (1.3): If y1′>x1 and y2′=x2, obviously, we have K1+G(Y′)⩾K1+G(Y1(x2), x2).
The three subcases mean that to increase inventory X to (Y1(x2), x2) is optimal in this case.
(2) For the case X∈O2, the proof is similar to that of the part (1).
(3) For the case X∈O12, the proof is similar to that of Theorem 1.
(4) For the case X∈O, clearly we have
and we also have
So, the optimal action is to choose one Y from (x1, Y2(x1)) and (Y1(x2), x2) such that V(Y) achieves the minimal value.
(5) For the case X∈Ō, the proof is similar to that of Theorem 1.
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Liu, K., Li, JA., Wu, Y. et al. Analysis of monitoring and limiting of commercial cheating: a newsvendor model. J Oper Res Soc 56, 844–854 (2005). https://doi.org/10.1057/palgrave.jors.2601913
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DOI: https://doi.org/10.1057/palgrave.jors.2601913