$400 million, respectively. Also contributing to the decrease were higher depreciation expenses of $1.0 billion, mainly related to impairments and other asset writeoffs, and higher operating and tax expenses of $340 million and $310 million, respectively. Partially offsetting these items were gains on asset sales of $1.1 billion in 2014, compared with $140 million in 2013. Foreign currency effects increased earnings by $597 million in 2014, compared with an increase of $559 million a year earlier.

International upstream earnings were $16.8 billion in 2013 compared with $18.5 billion in 2012. The decrease was mainly due to the absence of 2012 gains of approximately $1.4 billion on an asset exchange in Australia and $600 million on the sale of an equity interest in the Wheatstone Project, lower crude oil prices of $500 million, and higher operating expense of $400 million. Partially offsetting these effects were lower income tax expenses of $430 million. Foreign currency effects increased earnings by $559 million in 2013, compared with a decrease of $275 million a year earlier.

The company’s average realization for international crude oil and natural gas liquids in 2014 was $90.42 per barrel, compared with $100.26 in 2013 and $101.88 in 2012. The average natural gas realization was $5.78 per thousand cubic feet in 2014, compared with $5.91 and $5.99 in 2013 and 2012, respectively.

International net oil-equivalent production was 1.91 million barrels per day in 2014, a decrease of 2 percent from 2013 and 2012. Production increases due to project ramp-ups in Nigeria, Argentina and Brazil in 2014 were more than offset by normal field declines, production entitlement effects in several locations and the effect of asset sales. The decline between 2013 and 2012 was a result of project ramp-ups in Nigeria and Angola in 2013 being more than offset by normal field declines.

The net liquids component of international oil-equivalent production was 1.25 million barrels per day in 2014, a decrease of approximately 2 percent from 2013 and a decrease of approximately 4 percent from 2012. International net natural gas production of 3.9 billion cubic feet per day in 2014 was down 1 percent from 2013 and up 1 percent from 2012.

Refer to the “Selected Operating Data” table, on page FS-11, for a three-year comparative of international production volumes.

U.S. Downstream

U.S. downstream operations earned $2.6 billion in 2014, compared with $787 million in 2013. Higher margins on refined product sales increased earnings $830 million. Gains from asset sales were $960 million in 2014, compared with $250 million a year earlier. Higher earnings from 50 percent-owned CPChem of $160 million and lower operating expenses of $80 million also contributed to the earnings increase.

U.S. downstream operations earned $787 million in 2013, compared with $2.0 billion in 2012. The decrease was mainly due to lower margins on refined product sales of $860 million and higher operating expenses of $600 million, reflecting repair and maintenance activities at the company's refineries. The decrease was partially offset by higher earnings of $150 million from 50 percent-owned