When rejecting Job Candidates it is useful to record the reason for why the applicant was unsuccessful (read more about how to set up Rejection reasons). It can also be helpful to report on this rejection data later.
You can report on Rejection reasons using the 'Recruitment - Candidates' dataset in Reporting > Report builder.
Under the Candidate - other information section you'll find the field 'Rejection reason' which you can can include in your report.
To further drill down your results, to only display Candidates that have been rejected for example, you can include a Filter of 'Rejection reason equals' and select the rejection reasons you want to report on.