Oil prices settled slightly lower on Friday, the year's last trading day, but attained their biggest annual gain since 2009, after OPEC and partners agreed to cut output to reduce a supply overhang that has depressed prices for two years.
Oil prices settled slightly lower on Friday, the year's last trading day, but attained their biggest annual gain since 2009, after OPEC and partners agreed to cut output to reduce a supply overhang that has depressed prices for two years.