in 2014 primarily due to lower crude oil volumes, and lower refined product and crude oil prices. The decrease between 2013 and 2012 was mainly due to lower refined product prices and lower crude oil volumes and prices.

Income from equity affiliates

Income from equity affiliates decreased in 2014 from 2013 mainly due to lower upstream-related earnings from Tengizchevroil in Kazakhstan, Petropiar and Petroboscan in Venezuela, and Angola LNG. Partially offsetting these effects were higher downstream-related earnings from GS Caltex in South Korea, higher earnings from CPChem and the absence of 2013 impairments of power-related affiliates.

Income from equity affiliates increased in 2013 from 2012 mainly due to higher upstream-related earnings from Tengizchevroil in Kazakhstan and Petropiar in Venezuela, and higher earnings from CPChem, partially offset by 2013 impairments of power-related affiliates.

Refer to Note 13, beginning on page FS-40, for a discussion of Chevron’s investments in affiliated companies.

Other income of $4.4 billion in 2014 included net gains from asset sales of $3.6 billion before-tax. Other income in 2013 and 2012 included net gains from asset sales of $710 million and $4.2 billion before-tax, respectively. Interest income was approximately $145 million in 2014, $136 million in 2013 and $166 million in 2012. Foreign currency effects increased other income by $277 million in 2014, while increasing other income by $103 million in 2013 and decreasing other income by $207 million in 2012.

Crude oil and product purchases of $119.7 billion were down in 2014 mainly due to lower crude oil and refined products prices, along with lower crude oil volumes. Crude oil and product purchases in 2013 decreased by $6.1 billion from the prior year, mainly due to lower prices for refined products and lower volumes for crude oil, partially offset by higher refined product volumes.

Operating, selling, general and administrative expenses

Operating, selling, general and administrative expenses increased $642 million between 2014 and 2013. The increase included higher employee compensation and benefit costs of $360 million, primarily related to a buyout of a legacy pension obligation. Also contributing to the increase was higher transportation costs of $350 million, primarily reflecting the economic buyout of a long-term contractual obligation, and higher environmental expenses related to a mining asset of $300 million. Partially offsetting the increase were lower fuel expenses of $360 million.

Operating, selling, general and administrative expenses increased $1.8 billion between 2013 and 2012 mainly due to higher employee compensation and benefits costs of $720 million, construction and maintenance expenses of $590 million, and professional services costs of $500 million.

Exploration expense

Exploration expenses in 2014 increased from 2013 mainly due to higher charges for well write-offs, partially offset by lower geological and geophysical expenses. Exploration expenses in 2013 increased from 2012 mainly due to higher charges for well write-offs.

Depreciation, depletion and amortization

Depreciation, depletion and amortization