As one would expect, immigration from Australia, New Zealand's nearest neighbour, has at times been substantial. Many of the early settlers were from Australia, and the regular flow was strongly reinforced by the “Australian invasion” during the gold rush of the sixties. There have been periods also when the net flow of migrants has been from New Zealand to Australia. Economic conditions in the two countries are the major determinants of the direction of net migration. The yearly movements in net migration for just over 100 years are shown in Diag. 3.

The following census results show the number of persons in New Zealand who were born in Australia: 1867, 11,313; 1871, 12,426; 1874, 13,601; 1878, 16,091; 1881, 17,277; 1886, 17,245; 1891, 15,943; 1896, 21,631; 1901, 26,901; 1906, 47,256; 1911, 50,693; 1916, 45,585; 1921, 48,045; 1936, 42,009; 1945, 36,789; 1951, 35,828; 1956, 35,916; 1961, 35,412. As evidence of total immigration from Australia, this tabulation, however, is misleading since it covers only Australians – that is, persons born in Australia. A great many of the arrivals from Australia, particularly in the early years, were persons born in the British Isles who first settled in Australia and then moved on to New Zealand. For instance, although there were only 11,313 Australians in the population in 1867, the total net migration from Australia for the period 1861–67 exceeded 50,000.

The principal early contribution of Australia to New Zealand's population occurred prior to 1867. There was a small flow to Australia in the New Zealand depression of the late eighties, and a large intake of Australians during the prolonged Australian depression in the early 1900s. (From 1900 to 1908 the net gain to New Zealand exceeded 51,000.) The gain from Australia never again reached these proportions and consequently the numbers of Australians in the New Zealand population have since declined. In 1867, 6·9 per cent of persons born outside New Zealand were Australians; at the peak in 1911 the figure was 16·5 per cent, and in 1961, 10·4 per cent. Migrants who came from Australia in the early years of this century make up quite a large proportion of the Australians now resident in New Zealand. The 1961 census showed that 42·1 per cent of Australians had resided here for more than 40 years, and 19·4 per cent for between 20 and 40 years. In the 15 years ended March 1965 the net movement was in favour of New Zealand by some 27,860, of which the two years ended March 1963 accounted for more than 10,300, largely as a result of the Australian recession of 1961–62. In only three of the last 15 years has the net flow been in favour of Australia.