Note the interconnection of oil prices, the US dollar and political instability in Greece.
“Global oil prices on Monday collapsed under $50 for the first time in more than five years on the strong dollar, plunging equities, demand worries and plentiful crude supplies.
The renewed slump came as the Dow index stood down more than 200 points and European equity markets lost more than two percent on fears of a Greek exit, or so-called Grexit, from the eurozone.”
IR Theory & Practice 