Global oil prices have fallen sharply over the past seven months, leading to significant revenue shortfalls in many energy exporting nations, while consumers in many importing countries are likely to have to pay less to heat their homes or drive their cars. From 2010 until mid-2014, world oil prices had been fairly stable, at around 110 a barrel. But since June prices have more than halved.Brent crude oi has now dipped below 50 barrel for the first time since May 2009 and US crude is down to below 48 a barrel. The reasons for this change are twofold - weak demand in many countries due to insipid economic growth, coupled with surging US production. Added to this is the fact that the oil cartel Opec is determined not to cut the production as a way to prop up prices.Russia is one of the world39s largest oil producers, and its dramatic interest rate hie 10 17 in support of its troubled underscores how heavily its economy depends on energy revenues, with oil and gas accounting for 70 of export incomes. Russia loses about 2bn in revenues for every dollar fall in the oil price, and the World Bank has warned that Russia39s economy would shrink by at least 0.7 in 2015 if oil prices do not recover.