Revolution and unrest have many causes. Very often, as now in the Middle East and N Africa (MENA), their strength is due to a wide range of economic, social and political factors combining to create a coalition of angry people.
Age profile is also a key factor. As shown in the above chart, based on CIA World Factbook data, they all have young populations. And as the CIA note:
"Age structure can be used to help predict potential political issues. For example, the rapid growth of a young adult population unable to find employment can lead to unrest".
Those countries currently in the frontline of unrest have some of the youngest median population ages in the world. Whilst the USA (green column) is at 37 years, and Japan (red)/Germany (purple) at 45 years:
• Yemen's median age is just 19 years
• Iraq, Egypt, Libya and Oman are all in the 20 - 25 year range
• Iran is at 27 years; Tunisia and Bahrain are at 30 years
This is perhaps another indication that current problems may not end quickly.
Note: Median age is the age which divides the population of a country into 2 equal groups