Key Performance Indicators for Recruitment Effectiveness
Many KPIs can be built for that. For example, the ratio of CVs submitted vs. CVs cleared on screening shows whether the position description has been made correctly or not. Another example is the ratio of offers given to accepted, which highlights if there is an issue regarding job content, location, salary, etc.
Additionally, considering the cost and cycle time for various media channels is important. Attrition at various levels, whether it be during onboarding, training, or forced exits, should also be monitored. The cost per employee is acceptable on an enterprise level as it indicates how much is spent on a particular activity.
It's recommended to read "APQC" metrics for a good understanding.