▼ By the early twentieth century the notion that ethnic populations would dissipate was a commonly held belief. However, after World War II, the modern world has seen an incredible resurgence in ethnic identities. Ethnic conflicts, mobilisations, and the political movements of the 1950s and 1960s served as a major catalyst in the diffusion of indigenous identities and rights. Consequently, indigenous groups in settler states, especially in North America, experienced population growth beyond the levels of natural demographic factors, that is, fertility, mortality and migration. Researchers attributed a significant proportion of this growth to changing patterns of ethnic identification, also referred to as ethnic mobility . Although this phenomenon is well documented in North America, it is only just beginning to be understood in relation to the New Zealand context. During the 1970s and 1980s, the indigenous Māori population of New Zealand gained substantial progress in political, social and economic spheres, following the same patterns of ethnic identity growth as in North America. Despite these gains, the average individual socio-economic outcomes for Māori remain poor, especially in comparison to New Zealand Europeans/Pākehā. Through key legislation, iwi (tribal) organisations became the core mechanism in which to address Māori socio-economic issues, achieve Māori aspirations and to manage Treaty of Waitangi settlement monies. Subsequently, the need for iwi statistics for policy and planning purposes saw the reinstatement of iwi data in the New Zealand census in 1991. Surprisingly, however, very little attention has been given to contemporary patterns of iwi demography. Since the 1991 census, observations of total iwi population growth patterns indicate these patterns cannot solely be explained by natural demographic factors. Furthermore, the growth trajectories of individual iwi were markedly different, and in some cases erratic. These initial observations have raised the following key research questions: What do patterns of iwi growth look like? What is the role of ethnic mobility? What factors drive ethnic mobility? Who changes iwi identification? Why should we care? This thesis examines patterns of iwi identification in the New Zealand Census of Population and Dwellings from 1991 to 2006. It uses statistical methods to not only document iwi population changes but to also identify the key determinants driving these trajectories. In addition, this thesis considers ethnic mobility as an important driver of population growth but, situates this within the broader macro-political environment. Along with the analysis of aggregate iwi population changes, this thesis also provides an in-depth analysis of four iwi groups – Ngāi Tahu, Waikato, Ngāti Awa and Tūhoe, in order to observe individual iwi dynamics that are not clearly visible at the aggregate level. The findings of this thesis raise important implications for theories of ethnicity and the demographic study of ethnic populations. … Advisors/Committee Members: Kukutai, Tahu (advisor).