Tumult in Libya, U.S. rig counts, production plans of the oil exporting cartel and a pact on nuclear relations with Iran can all affect crude supply and demand, but oil traders have kept an equally close watch on retail investors in recent weeks. Those investors and hedge funds, betting on a reversal of oil’s long rout, poured billions of dollars into exchange traded products at the tail end of the slide last year, providing unexpected support that helped prices stabilize.