under random disruption risk,we compare the backup sourcing strategy with the manufacturer-initiated efficency-improvement effort sourcing strategy.Results show that,when the manufacturer purchases from the unreliable supplier,the optimal purchasing quantity under the manufacturer-initiated efficency-improvement effort sourcing strategy is always more than it under the backup strategy.The manufacturer’s revenue gap between the efficiencyimprovement effort sourcing strategy and backup sourcing strategy will decrease as the cost of effort increa...