income of $1.6 billion in 2016 included net gains from asset sales of $1.1 billion before-tax. Other income in 2015 and 2014 included net gains from asset sales of $3.2 billion and $3.6 billion before-tax, respectively. Interest income was approximately $145 million in 2016, $119 million in 2015 and $145 million in 2014. Foreign currency effects decreased other income by $186 million in 2016, and increased other income $82 million in 2015 and $277 million in 2014.

Crude oil and product purchases in 2016 and 2015 decreased from prior year periods by $10.4 billion and $49.9 billion, respectively, primarily due to lower crude oil and refined product prices, partially offset by an increase in crude oil volumes.

Operating, selling, general and administrative expenses decreased $2.5 billion between 2016 and 2015. The decrease included lower employee expenses of $800 million, transportation expenses of $680 million, contract labor expenses of $370 million, materials and supplies expenses of $310 million, and fuel expenses of $310 million.

Operating, selling, general and administrative expenses decreased $2.3 billion between 2015 and 2014. The decrease included lower fuel costs of $920 million. Also contributing to the decrease were lower expenses for construction, repair and maintenance of $300 million, contract labor of $270 million, and research, technical and professional services of $200 million.

Exploration expenses in 2016 decreased from 2015 primarily due to significantly higher 2015 charges for well write-offs largely related to project cancellations, and lower 2016 geological and geophysical expenses.

Exploration expenses in 2015 increased from 2014 primarily due to higher charges for well write-offs largely related to project cancellations.

Depreciation, depletion and amortization expenses decreased in 2016 from 2015 primarily due to lower impairments of certain oil and gas producing fields of about $3.0 billion in 2016 compared with about $3.5 billion in 2015. Also contributing to the decrease were lower production levels and accretion expenses for certain oil and gas producing fields.

The increase in 2015 from 2014 was primarily due to impairments of oil and gas producing fields of about $3.5 billion in 2015 compared with $900 million in 2014. Also contributing to the increase were higher depreciation rates and higher production levels for certain oil and gas producing fields.

Taxes other than on income decreased in 2016 from 2015 primarily due to lower refined product and crude oil prices, and the divestment of the Pakistan fuels business at the end of June 2015. Taxes other than on income decreased in 2015 from 2014 primarily due to lower crude oil and refined product prices.

The decline in income tax expense in 2016 of $1.86 billion is consistent with the decline in total income before-tax for the company of $7.00 billion.  U.S. losses before tax increased from a loss of $2.88 billion in 2015 to a loss of $4.32 billion in 2016. This $1.44 billion increase in losses was primarily driven by the effect of lower crude oil prices. The increase in losses had a direct impact on the company’s U.S. income tax benefit, resulting in an