No one could predict that the death of a Tunisian vegetable vendor would spark revolts across the Middle East, threatening regimes from Libya to Iran. But while these shockwaves might seem chaotic, they are in fact only the latest example of a powerful political phenomenon: the J-curve, or the dip in stability as countries move from closed to open societies. The concept also explains why many of the region’s governments are now caught in what may prove to be an inescapable trap.

The theory goes like this. If you plot the relationship between a country’s stability (on the vertical axis) and its social and political openness (on the horizontal axis) the points that mark every possible combination of openness and stability will produce a pattern that resembles the letter J. Most countries start off closed and stable (think: North Korea). Many end up open and stable (like Britain). But in between there is a turbulent transition. Some governments, such as post-apartheid South Africa, survive this transition. Others – the Soviet Union, Iran under the shah and the former Yugoslavia – do not.

This presents a dilemma for the Middle East. In recent years, globalisation has provided more young Arabs with access to education, media and travel – innovations that make it more difficult for a ruling elite to control information and power. If governments, such as Egypt’s, relax their grip to stoke economic growth (by opening their societies to deeper integration with the outside world) they risk sharp social and political upheaval. Yet if they keep things closed, they sharply limit the power of their economies to generate the prosperity on which longer-term political legitimacy will depend. And that too creates instability.