Grouping of age according to the following rules:
00X - Less than 7 days old (where X is the number of days)
01X - Between 1 and 3 weeks old (where X is the number of weeks)
1XX - Between 1 and 11 months old (where XX is the number of months old)
2XX - Between 1 and 99 years old (where XX is the number of years old)
3XX - Over 99 years old (where XX is the number of years over 100)

In reporting environment allows grouping of ages into clinically meaningful groups with greater definition for the young age groups than would occur from simply reporting age in years.