For every 10$ drop in the price of oil, Russia is losing 14.6 billion dollars a year in revenue (International Business Times). Let’s round it up to 15 billion dollars a year to make it easy to remember. For every 10$ drop in the price of oil Russia is losing 15$ billion a year i.e. 10-15.
That means that for every 1$ drop in oil prices Russia is losing 1.5 billion dollars per year.
“How The World’s Biggest Oil Exporters Are Suffering From $40-A-Barrel Crude Oil”, August 2015