Russian state-controlled oil company OAO Rosneft reported a slight increase in full-year net profit, shielded from plunging oil prices that battered the results of western oil producers by a weakening ruble and a tax system that eases as prices fall. Rosneft, the world’s largest listed crude producer, said Thursday that net income rose 2% to 355 billion rubles (about $6.1 billion) in the year to end-December. Other global oil groups such as Exxon Mobil Corp. and Royal Dutch Shell PLC reported significantly poorer results on lower oil prices , down to around $40 a barrel at the end of last year from nearly $70 at the start. Rosneft’s results demonstrate the resilience of Russia’s oil industry, a critical source of revenue for the federal budget when the economy is also being squeezed by western […]