Demographic theories can be grouped into two classes, Malthusian theories and youth bulge theories.
Malthusian theories see expanding population and scarce resources as a source of violent conflict.
Pope Urban II in 1095, on the eve of the First Crusade, wrote, "For this land which you now inhabit, shut in on all sides by the sea and the mountain peaks, is too narrow for your large population; it scarcely furnishes food enough for its cultivators. Hence it is that you murder and devour one another, that you wage wars, and that many among you perish in civil strife. Let hatred, therefore, depart from among you; let your quarrels end. Enter upon the road to the Holy Sepulcher; wrest that land from a wicked race, and subject it to yourselves."
This is one of the earliest expressions of what has come to be called the Malthusian theory of war, in which wars are caused by expanding populations and limited resources. Thomas Malthus (1766–1834) wrote that populations always increase until they are limited by war, disease, or famine.
This theory is thought by Malthusians to account for the relative decrease in wars during the past fifty years, especially in the developed world, where advances in agriculture have made it possible to support a much larger population than was formerly the case, and where birth control has dramatically slowed the increase in population.
Youth bulge theory differs significantly from malthusian theories. Its adherents see a combination of large male youth cohorts (as graphically represented as a "youth bulge" in a population pyramid) with a lack of regular, peaceful employment opportunities as a risk pool for violence. While malthusian theories focus on a disparity between a growing population and available natural resources, youth bulge theory focuses on a disparity between non-inheriting, "excess" young males and available social positions within the existing social system of division of labour.
Contributors to the development of youth bulge theory include French sociologist Gaston Bouthoul,,[10] U.S. sociologist Jack A. Goldstone,,[11] U.S. political scientist Gary Fuller,,[12][13][14] and German sociologist Gunnar Heinsohn.[15] Samuel Huntington has modified his Clash of Civilizations theory by using youth bulge theory as its foundation:
I don't think Islam is any more violent than any other religions, and I suspect if you added it all up, more people have been slaughtered by Christians over the centuries than by Muslims. But the key factor is the demographic factor. Generally speaking, the people who go out and kill other people are males between the ages of 16 and 30. During the 1960s, 70s and 80s there were high birth rates in the Muslim world, and this has given rise to a huge youth bulge. But the bulge will fade. Muslim birth rates are going down; in fact, they have dropped dramatically in some countries. Islam did spread by the sword originally, but I don't think there is anything inherently violent in Muslim theology."[16]
Youth Bulge theories represent a relatively recent development but seem to have become more influential in guiding U.S. foreign policy and military strategy as both Goldstone and Fuller have acted as consultants to the U.S. Government. CIA Inspector General John L. Helgerson referred to youth bulge theory in his 2002 report "The National Security Implications of Global Demographic Change".[17]
According to Heinsohn, who has proposed youth bulge theory in its most generalized form, a youth bulge occurs when 30 to 40 percent of the males of a nation belong to the "fighting age" cohorts from 15 to 29 years of age. It will follow periods with total fertility rates as high as 4-8 children per woman with a 15-29 year delay. A total fertility rate of 2,1 children born by a woman during her lifetime represents a situation of in which the son will replace the father, the daughter the mother. Thus, a total fertility rate of 2,1 represents replacement level, while anything below represents a sub-replacement fertility rate leading to population decline. Total fertility rates above 2,1 will lead to population growth and to a youth bulge. A total fertility rate of 4-8 children per mother implies 2-4 sons per mother. Consequently, one father has to leave not 1, but 2 to 4 social positions (jobs) to give all his sons a perspective for life, which is usually hard to achieve. Since respectable positions cannot be increased at the same speed as food, textbooks and vaccines, many "angry young men" find themselves in a situation that tends to escalate their adolescent anger into violence: they are
- demographically superfluous,
- might be out of work or stuck in a menial job, and
- often have no access to a legal sex life before a career can earn them enough to provide for a family.
The combination of these stress factors according to Heinsohn[18] usually heads for one of six different exits:
- Violent Crime
- Emigration ("non violent colonization")
- Rebellion or putsch
- Civil war and/or revolution
- Genocide (to take over the positions of the slaughtered)
- Conquest (violent colonization, frequently including genocide abroad).
Religions and ideologies are seen as secondary factors that are being used to legitimate violence, but will not lead to violence by themselves if no youth bulge is present. Consequently, youth bulge theorists see both past "Christianist" European colonialism and imperialism and today's "Islamist" civil unrest and terrorism as results of high birth rates producing youth bulges.[19] While during the period of European colonialism, European countries had high birthrates and huge youth bulges that fueled colonialist expansion, today Afghanistan, which has a total fertility rate of 6 children per woman and an estimated unemployment rate of 40%,[20] would represent a typical youth bulge country.[21] The Gaza Strip can be seen as another example of youth-bulge-driven violence, especially if compared to Lebanon which is geographically close, yet remarkably more peaceful.[22] Among prominent historical events that have been linked to the existence of youth bulges is the role played by the historically large youth cohorts in the rebellion and revolution waves of early modern Europe, including French Revolution of 1789,[23] and the importance of economic depression hitting the largest German youth cohorts ever in explaining the rise of Nazism in Germany in the 1930s.[24] The 1994 Rwandan Genocide has also been analyzed as following a massive youth bulge.[25]
While the security implications of rapid population growth have been well known since the completion of the National Security Study Memorandum 200 in 1974,[26] neither the U.S. nor the WHO have effectively implemented the recommended preventive measures to control population growth to avert the terror threat they are now facing. Prominent demographer Stephen D. Mumford attributes this to the influence of the Catholic Church.[27]
Youth Bulge theory has been subjected to statistical analysis by the World Bank,[28] Population Action International,[29] and the Berlin Institute for Population and Development.[30] Detailed demographic data for most countries is available at the international database of the United States Census Bureau.[31]
Youth bulge theories have been criticized as leading to racial, gender and age discrimination
