prostate cancer remained constant, even though the incidence increased, so the additional reported prostate cancers did not represent an increase in real prostate cancers, said Hsing. Similarly, the death rates from prostate cancer in the U.S. increased during the 1980s and peaked in early 1990. This is at least partially due to "attribution bias" on death certificates, where doctors are more likely to ascribe a death to prostate cancer than to other diseases that affected the patient, because of greater awareness of prostate cancer or other reasons. Because health status is "considerably affected" by socioeconomic and demographic characteristics, such as level of education and income, "the value of comparisons in isolating the impact of the healthcare system on outcomes is limited," according to health care analysts. Experts say that the incidence and mortality rates of cancer cannot be combined to calculate survival from cancer. Nevertheless, researchers have used the ratio of mortality to incidence rates as one measure of the effectiveness of healthcare. Data for both studies was collected from registries that are members of the North American Association of Central Cancer Registries, an organization dedicated to developing and promoting uniform data standards for cancer registration in North America. Racial and ethnic differences The U.S. and Canada differ substantially in their demographics, and these differences may contribute to differences in health outcomes between the two nations. Although both countries have white majorities, Canada has a proportionately larger immigrant minority population. Furthermore, the relative size of different ethnic and racial groups vary widely in each country. Hispanics and peoples of African descent constitute a much larger proportion of the U.S. population. Non-Hispanic North American aboriginal peoples constitute a much larger proportion of the Canadian population. Canada also has a proportionally larger South Asian and East Asian population. Also, the proportion of each population that is immigrant is higher in Canada. A study comparing aboriginal mortality rates in Canada, the U.S. and New Zealand found that aboriginals in all three countries had greater mortality rates and shorter life expectancies than the white majorities. That study also found that aboriginals in Canada had both shorter life expectancies and greater infant mortality rates than aboriginals in the United States and New Zealand. The health outcome differences between aboriginals and whites in Canada was also larger than in the United States. Though few studies have been published concerning the health of Black Canadians, health disparities