Few commodities are as powerful as oil. Its value can make or break governments, causing growth or economic hardship, depending on which way the price swings. The plunging value of crude is having a negative impact on a few, but is a positive shift for the majority, China prominent among them. But it is wrong for medium or long-term planning to be based on the drop: any number of factors, political, social and technological among them, makes predicting the value futile. The price of benchmark Brent light crude has fallen more than 40 per cent since June, when it was US$115 a barrel. Sluggish growth in Asian and European economies has decreased demand, US production has increased and vehicles that are more fuel-efficient are taking to the world's roads in ever-rising numbers. The oil cartel Opec, with Saudi Arabia in the driving seat, has maintained high levels of output to counter the impact of the boom in American shale oil and protect market share. Insurgencies in oil producers Iraq, Libya, Nigeria and Syria are being ignored by traders. There are winners, but also big losers. The IMF estimates that global GDP grows by 0.2 per cent for every 10 per cent fall in the oil price; a drop puts more money in the pockets of governments and consumers, boosting spending. China, the world's second-biggest net importer, saves US$2.1 billion for every US$1 decline, while there will be hefty budget gains for Indonesia and India, countries that heavily subsidise oil. That should make imports cheaper, foreign currency go further and, over time, living standards rise. Chief among the losers are oil producers, which have relied on high prices to drive their policies, Iran, Russia and Venezuela being the most vulnerable. Iran's budget is based on oil being priced at US$140 a barrel and Venezuela's at US$120, worsening inflation and exacerbating shortages of everyday goods. Russia is less vulnerable due to its hefty fiscal reserves, but should oil prices remain low for two or more years, the economic consequences would be dire.