The Federal Reserve (FR) has been inflating the dollar by buying $80 billion a month of treasury bonds. When a currency is inflated, it's value relative to the goods and services it can buy (bonds, oil, gas, pork bellies, stock in USELESS companies like facebook and Alibaba...i.e., everything) goes down while the relative value of the goods and services go up.
The FR purchasing program is set to terminate at the end of October, so the process is now reversing itself.