Portugal has suffered an impressive decline in fertility (from 3.2 children per woman in 1960, to 1.2 in 2014), along with an increase in longevity (an almost 15 years increase in life expectancy between 1960 and 2013). This has produced an aged population, with a large old age dependency ratio: Eurostat estimates that there were 30.3 people aged 65+ per 100 people aged 15-64 in 2014. Despite the decreasing numbers of young dependents,a rising overall dependency ratio has existed since the beginning of this century. Simultaneously, both gross domestic product (GDP) and GDP per capita growth rates have been low, or even negative during the 2000’s. Naturally, there are many reasons for this, but what is the influence of demography on economic growth? Should we expect the ageing of population to be playing a positive or a negative role? Can we blame it for at least a small proportion of our economic woes? During the 19th and 20th Centuries, there were opposing views about the impact of demography on economic growth. The existence of diminishing returns to labour would imply that an ever-increasing number of workers would not be accompanied by a growth rate of output at the same pace, therefore leading to decreasing output per capita. Two authors that fit in with this line of thought are Malthus and Ehrlich. Another argument that defends that population growth is adverse to economic growth can be found in the growth model of Solow, where a high population growth tends to decrease capital per worker (capital dilution), thus reducing economic growth. On the other hand, Keynes and Alvin Hansen defended that population growth is an important source of economic progress, creating growing demand and investment incentives. A shrinking population produces smaller incentives for investment and the economy would therefore stagnate – which is known as secular stagnation. This type of argument, which links population size and growth to economies of scale, innovation and technological progress was common amongst other authors (Simon 1977 [as cited in Boulier 1979] and Kremer 1993, for example). Empirical studies (Kuznets 1967, Kelley 1988) had trouble finding robust evidence to support any of these positions and subsequent research settled on a population neutralism (Bloom and Canning 2006) that considered that population growth cannot explain the differences in growth rates of different countries. However, when not only total population growth was considered, but also its age structure, the importance of demographics started to show (Lindh and Malmberg 1999, Prskawetz et al. 2007). It is not so much the size of the population that matters, but its age structure. There are three main ways that population ageing influences economic growth: labour supply, savings and investment, and productivity