Population statistics

Worldwide, birthrates have been halved in the past 50 years. There are now 59 nations, with 44% of the world's population, with below-replacement fertility. In this century, the world's population will begin to decline. At a certain point, the decline will become rapid. We may even reach population free-fall in our lifetimes. For some countries, population decline is already a reality. Russia is losing three-quarters-of-a-million people a year. Its population (currently 145million) is expected to fall by one-third by 2050. 

United Nations World Population Ageing Report  

In 2007, the United Nations released its global population estimates in a report entitled World Population Ageing revealing an alarming population shift that will have serious world-wide consequences within the near future. The report indicates that people above 60 years old are starting to outnumber children, those under age 15. By 2047 old people will outnumber children on a global scale, the report states, although developed countries already reached this mark in 1998.

By the year 2000 the number of old people had tripled in the world since 1950. Only six year later, they had increased by another 100 million. The rate of their increase is 2.6% per year versus the 1.1% increase of the rest of the population. In addition, even those over 60 years are aging, and the number of people aged 80+ is most rapidly increasing.

At present the median age worldwide is 28 years, a number that is expected to rise to 38 by 2050. The oldest country is Japan, with a median age of 43, while the youngest is Uganda, with a median age of 15.

Read a summary of the UN population report here

http://www.un.org/esa/population/publications/WPA2007/wpp2007.htm

Consequences of a demographic  decline

These numbers will have a serious effect on the working population, which will be forced to bear an increasingly heavy burden of retirees. By 2050 the ratio of workers between 15 and 64 to older persons will have decreased from 12 to 1 in 1950 to a mere 4 to 1.

Western Europe's population grows dramatically grayer. Now about one-sixth of the population is 65 and older. By 2030, that could be one-fourth and by 2050, almost one-third.

By the mid-point of this century, 16% of the world's population will be over 65. By 2040, there will 400 million elderly Chinese who had no children to look after them. If present low birthrates persist, the European Union estimates there will be a continent-wide shortfall of 20 million workers by 2030. 

Who will operate the factories and farms of the future. Who will develop natural resources. Who will care for a graying population? A burgeoning elderly population combined with a shrinking work force will lead to a train-wreck for state pension systems. 

This only skims the surface of the way demographic decline will change the face of civilization.