Services outsourcing under asymmetric cost information

•We analyze a service supply chain where client firm sources from a set of vendors.•Vendor’s variable cost structure is private information.•We find as cost variation increases, optimum number of vendors decreases.•We find a threshold policy of impact of demand uncertainty on size of vendor base. In this paper, we investigate the impact of cost heterogeneity on the optimal sourcing strategy of a client firm that outsources her service requirements to a set of outside vendors/service providers. We analyze a typical situation involving service providers, who differ from one another with respect to the marginal cost and characterize the firm’s optimal size of vendor network. In our model, the client firm does not have complete information about the vendors’ cost structure. From the client firm’s perspective, for the case when the open market demand distribution is Uniform and the buyer’s demand is Normally distributed, we analytically derive the capacity to be procured as well as and the optimal number of vendors to be awarded the contract. Our analysis reveals that with an increase in vendor base cost heterogeneity, the optimum number of required vendors decreases. We further conclude that when the mean demand of the client firm is below a threshold value, then as the client firm’s demand variability increases, the optimal number of vendors increases. Whereas, in case the client firm’s mean demand is above the threshold value, then the optimal size of vendor base decreases as the client firm’s demand variability increases.