I have worked on the client and the outsourcer side of this equation. Several factors can impact actual vs planned staffing and other critical factors that are related such as utilization rates, handle times, success rates, meeting SLAs, etc.
Several variables will be beyond your control, however depending on your application (outbound/inbound) and the contract terms (penalties/incentives), you can control the compensation set-up, SLA objectives, list penetration, volume forecast, etc. Of course there is no substitute for great client/vendor communication to make sure both parties understand the objectives and challenges to meeting them.
Please feel free to contact me if you would like to discuss
Clint
402-486-4608
csesow@calltech.com