Over the period 2001-2013, Portugal experienced a decrease in both natural change and net migration, which became negative. Fertility remains at levels far below those necessary to renew the generations and the country reaches a level of “lowest-low fertility” although longevity increases and life expectancy gap between men and women narrows. The effects of the evolution of demographic variables on population age structure strengthen the process of demographic ageing.

The new family models in Portugal are the result of the significant fall in the number of marriages and the strong rise of the number of wedlock births, the average age at marriage and the number of divorces. This paper intends to study the patterns of demographic variables responsible for the major changes in both population size and age structure of the population and culminating in its significant ageing and negative population growth.

keywords: Population, Fertility, Mortality, Life expectancy, Migrations, Ageing