The size of an ethnic group can never be definitively determined because the concept of an ethnic group is elastic. There is an element of choice in immigrant situations where the only division is between citizens and non-citizens. Once Australia abandoned racial classification of immigrants, which it finally did in 1973, there was no official reason for delimiting ethnic groups.
Birthplace became an unsatisfactory surrogate for ethnicity, to be joined by religion in many cases and, from 1976, by language. To illustrate varying definitions of an ethnic group, some 1991 figures of birthplace, religion and language are given in the following table.