Yield ratios are calculated stage by stage: divide the number who reach the next stage by the number who entered the current one. If 200 people apply and 50 are screened in, the applied-to-screened yield is 25%. Tracking yields over several hiring rounds builds a benchmark, so a team can estimate how many applicants it needs to make one hire for a given role.
A low yield at one stage points to a specific fix. Few qualified applicants suggests the advert or channel needs work, while many interviews but few offers may mean the screening criteria do not match what the hiring manager wants. Yields should also be compared across groups at each stage, since a stage that loses one group faster than others needs review.