...en of childbearing age, i.e., 15 or 20 to 44 or 49, is used as an index of fertility when reliable birth statistics are not available. ...rtility rates|8|631|IndexEntry=age-specific fertility rate|OtherIndexEntry=fertility rate, age-specific}} or {{TextTerm|age-specific birth rates|8|631|2|IndexEn

...f these rates will refer to different periods of time. Where statistics of fertility by age are not available, the so-called {{TextTerm|replacement index|8|711| ...thin this group in the life table is known as the {{NoteTerm|net fertility schedule}}.