The ruble has sunk 19 percent this month to 61 per dollar even after posting a 10 percent rebound on Wednesday triggered by the government's sale of dollars and central bank measures to help companies refinance looming foreign-currency debt. The currency's down 46 percent this year through yesterday, the result of tumbling prices for oil, Russia's top export, and international sanctions tied to the Ukraine conflict.
I can't find the subject and verb in that sentence. Is currency's in the possessive case or is 's just a contraction form of is? Which part of the sentence is Russia's top export grammatically aligned with?