Formula For Recruitment Effectiveness

Hi all,
I am deriving a formula to find recruitment effectiveness.
Can some one help me understand what are the cost involved in recruitment.
I also wanna know whether cost/employee should be included.

many KPIs can be built for that
eg
ratio of cvs submitted vs CVs cleared on screening, this shows whether position description has been made correctly or not..
ratio of offers given to accepted, highlights if we have an issue regarding job content/ location/ salary etc
cost n cycle time for various media
attrition at various levels be it onboarding or training or forced exits
cost per employee is ok on an enterprise level.. as to how much is the spend on a particular activity.
read "APQC" metrics for a good understanding