Background Breast cancer incidence varies between social groups, but differences have not
been thoroughly examined in New Zealand. The objectives of this study are to determine
whether trends in breast cancer incidence varied by ethnicity and socioeconomic position
between 1981 and 2004 in New Zealand, and to assess possible risk factor explanations.
Methods Five cohorts of the entire New Zealand population for 1981-86, 1986-1991, 1991-
1996, 1996-2001, and 2001-2004 were created, and probabilistically linked to cancer …

Background Breast cancer incidence varies between social groups, but differences have not
been thoroughly examined in New Zealand. The objectives of this study are to determine
whether trends in breast cancer incidence varied by ethnicity and socioeconomic position
between 1981 and 2004 in New Zealand, and to assess possible risk factor explanations.
Methods Five cohorts of the entire New Zealand population for 1981-86, 1986-1991, 1991-
1996, 1996-2001, and 2001-2004 were created, and...