Final answer:
The factor contributing to the short-term costs of employing contingent workers is training and onboarding expenses, as these incur both direct and indirect costs and may lead to a temporary decline in productivity.
Step-by-step explanation:
The short-term costs of engaging contingent workers include training and onboarding expenses. When a company employs contingent workers, they often need to invest in training these individuals to ensure they perform effectively. This process incurs direct costs like materials and trainers, and indirect costs through the loss of productivity as new workers come up to speed.
Moreover, contingent workers may lack the company-specific knowledge and experience of regular employees, which can result in a temporary decline in productivity and efficiency. Recruitment expenses are generally lower for contingent workers, and firms indeed gain workforce flexibility and avoid long-term commitments. Hence, among the given options, the factor that contributes to the short-term costs for engaging contingent workers is training and onboarding.