Readmissions are cases where a patient is discharged from the hospital, but then needs to be readmitted within a certain amount of time, usually 30-days. The readmission ratio compares the rate of readmissions to the hospital compared to the expected rate of hospital readmissions based on national averages. A ratio of 1.0 is what would be expected based on certain medical problems and illnesses. A ratio less than 1 is lower than expected, while a ratio greater than 1 is higher than expected.