Her research spans a broad range of population topics from iwi /tribal demography and indigenous data sovereignty, to Māori-migrant relations and the impacts of colonisation on Indigenous health. She has undertaken commissioned work for numerous iwi entities, Māori organisations, and government policy agencies.
Much of her research uses mixed methods and involves working with other social scientists in Aotearoa and internationally. Current projects include: Counting our Tūpuna: Colonisation and indigenous survivorship in Aotearoa NZ (Marsden Fund); Indigenous data sovereignty: Enduring aspirations in a digital age (Ngā Pae o Te Māramatanga); Indigenous health in transition (Swedish Research Council, PI: AProf. Per Axelsson); and Capturing the diversity dividend in Aotearoa New Zealand (Ministry of Business, Innovation and Employment: PI: Prof. Jacques Poot & Prof. Paul Spoonley).
In addition to her work in Māori and Indigenous demography, Tahu leads the Ethnicity Counts? project which studies how governments around the world count and classify populations by ethnic-racial criteria and citizenship status. She has published widely on this topic, as well as on census methodologies, with Dr Victor Thompson (Rider University, USA). They are currently writing a book examining how and why state practices of ethnic-racial and civic enumeration have changed over the past 30 years.