According to the 2006 Census, almost the Canadian population were foreign-born, a percentage that is projected to reach at least 25% by 2031. Studies based on age-standardized mortality rates (ASMR) have found a healthy immigrant effect, with lower overall rates among immigrants. A duration effect has also been observed-immigrants' mortality advantage lessened as their time in Canada increased. ASMRs based on the 1991 to 2001 census mortality follow-up study indicate a healthy immigrant effect and a duration effect at the national level for all-cause mortality for both sexes. However, at the national level, the mortality rate among women from the United States and from Sub-Saharan Africa was similar to that of Canadian-born women. For the three largest Census Metropolitan Areas (Toronto, Montreal and Vancouver), a healthy immigrant effect was not observed among women or among most men from the United States or Sub-Saharan Africa.