What happens to economic activity with population ageing? And, crucially, what happens in the context of free mobility of labour, currency union and open trade and capital mobility? These are the questions to be answered for European policymakers, facing rapid increases in population age and in some countries (Germany and Italy already) facing decreases in working age population.
An interesting paper on the subject was just published in the U.S. authored by Maestas, Nicole and Mullen, Kathleen and Powell, David, study titled "The Effect of Population Aging on Economic Growth" (October 2014, RAND Working Paper Series WR-1063: http://ssrn.com/abstract=2533260).
Per authors, "Population aging is widely expected to have detrimental effects on aggregate economic growth. However, we have little empirical evidence about the actual existence or magnitude of such effects. In this paper, we exploit differential aging patterns at the state level in the United States between 1980 and 2010. Many states have already experienced high growth rates of the 60 population, comparable to the predicted national growth rate over the next several decades. Furthermore, these differential growth rates occur partially for reasons unrelated to economic growth, providing a natural approach to isolate the impact of aging on growth."
The study predicts "the magnitude of population aging at the state-level given the state’s age structure in an initial period and exploit this predictable differential growth to estimate the impact of population aging on Gross Domestic Product (GDP) growth, and its constituent parts, labor force and productivity growth."
The result is an estimate showing "that a 10% increase in the fraction of the population ages 60 decreases GDP per capita by 5.7%. We find that this reduction in economic growth caused by population aging is primarily due to a decrease in growth in the supply of labor. To a lesser extent, it is also due to a reduction in productivity growth. We present evidence of downward adjustment of earnings growth to reflect the reduction in productivity."