[5] The governments of these countries have made financial commitments to the elderly in their populations which will consume huge percentages of their national GDP.
[7] The demographic transition from the late eighteenth century onwards opened up the possibility that significant change could occur within and between political units.
This has come about due to medical advances which have lowered infant mortality while conquest migrations have faded as a factor in world history.
It is not so much the trajectory of demographic transition that counts as the fact that it has become more intense and uneven in the late twentieth century as it has spread into the developing world.
These changes are in turn, magnified by democratization, which entrenches majority rule and privileges the power of numbers in politics as never before.
Ethnic parties struggle to increase their constituencies through pronatalism ('wombfare'), oppose family planning, and contest census and election results.
[12] Irish Catholics in Northern Ireland increased their share of the population through higher birthrates and the momentum of a youthful age structure from 35 to nearly 50 percent of the total between 1965 and 2011.
Similar changes, also affected by in- and out-migration, have taken place in, amongst others, the United States (Hispanics), Israel-Palestine (Jews and Arabs), Kosovo (Albanians), Lebanon (Shia, with decline of Christians) and Nagorno-Karabakh (Armenians).
In general, youth bulges in developing countries are associated with higher unemployment and, as a result, a heightened risk of violence and political instability.
However, like those under-16, they place great strain on the social safety net, especially in countries committed to old-age provision and high-quality medical care.
[18] Others are concerned that population aging will bankrupt the welfare state and handicap western liberal democracies' ability to project power abroad to defend their interests.