Saudi Arabia took $2 billion a week out of its foreign reserves between the end of September last year and June this year. Saudi Arabia's monetary agency put its foreign reserves at $672b at the end of June, down from $746bn in September last year. The world's top oil exporter and the de facto leader of the 12-nation OPEC cartel, Saudi Arabia has shown in the past that it is prepared to use oil money to quell social unrest. It was able to nip Arab Spring protests in the bud by paying off demonstrators and spending $130bn to raise salaries and boost social spending.
On the plus side, a lower oil price has boosted the world economy by diverting consumer spending away from energy costs. "The world's consumers will be much better off, especially the poor, who spend a higher proportion of their income on energy," Professor Leif Wenar said at King's College London
"Big importers such as India, China, Japan and many developing countries will be winners. It should help growth and cut the cost of basic goods," he stressed.In Venezuela, which has the world's biggest oil reserves, the opposite applies. The country is spiralling into hyperinflation and crime is rising amid fears of a debt default - all of which could bring an end to the presidency of Nicolas Maduro as early as December, when parliamentary elections are due to be held.
In Russia, where oil and gas account for 75 per cent of exports and more than half of budget revenues, a plunging economy and a struggling currency are threatening living standards - giving nourishment to nationalists and others eager to whip up an anti-Western war in Ukraine. For every dollar the oil price falls, Russia loses $2bn, according to Professor Wenar. "If prices stay low I expect more anti-Western rhetoric and a ramping up of the war, to distract public attention and heap blame on the West," he said. Russia's economy shrank 4.6 per cent in the second quarter, its worst performance since 2009.The smaller Middle Eastern and African oil exporters that lack Saudi Arabia's deep pockets are suffering worst. Algeria, which relies on oil and gas for 97 per cent of export revenues, is already battling an Islamist insurgency and could find itself overwhelmed, like neighbouring Libya, if its fragile economy crumbles.
Gulf states such as Bahrain and Oman, which rely heavily on Saudi cash and patronage, fear a revival of civil unrest or religious strife if the oil crisis drags on.
Iran, too, is feeling the pressure - one of the reasons why it was willing to strike a deal over its nuclear program.
Iraq's government is struggling to pay for its fight against Islamic State, which controls the leading city of Mosul and swathes of territory in the north of the country.
Other OPEC members such as Angola and Nigeria face deepening economic hardship, fuelling insurgencies from groups such as Boko Haram.
Saudi Arabia, where two thirds of the population is aged under 30, might face social upheaval in the near future, especially if an economic slump brings fewer jobs and opportunities for the young - and civil unrest would quickly fuel Islamist militancy.