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 expenses increased in 2014 from 2013 mainly due to higher depreciation rates and impairments for certain oil and gas producing fields, and the impairment of a mining asset. The increase in 2013 from 2012 was mainly due to higher depreciation rates for certain oil and gas producing fields, higher upstream impairments and higher accretion expense, partially offset by lower production levels.

Taxes other than on income

Taxes other than on income decreased in 2014 from 2013 mainly due to a decrease in duty expense in South Africa along with lower consumer excise taxes in Thailand, reflecting lower sales volumes at both locations. Taxes other than on income increased in 2013 from 2012 primarily due to the consolidation of the 64 percent-owned Star Petroleum Refining Company, beginning June 2012, and higher consumer excise taxes in the United States.

Income tax expense

Effective income tax rates were 38 percent in 2014, 40 percent in 2013 and 43 percent in 2012. The decrease in the effective tax rate between 2014 and 2013 primarily resulted from the impact of changes in jurisdictional mix and equity earnings, and the tax effects related to the 2014 sale of interests in Chad and Cameroon, partially offset by other one-time and ongoing tax charges.

The rate decreased between 2013 and 2012 primarily due to a lower effective tax rate in international upstream operations. The lower international upstream effective tax rate was driven by a greater portion of equity income in 2013 than in 2012 (equity income is included as part of before-tax income and is generally recorded net of income taxes) and foreign currency remeasurement impacts.

Liquidity and Capital Resources

Cash, Cash Equivalents, Time Deposits and Marketable Securities Total balances were $13.2 billion and $16.5 billion at December 31, 2014 and 2013, respectively. Cash provided by operating activities in 2014 was $31.5 billion, compared with $35.0 billion in 2013 and $38.8 billion in 2012. Cash provided by operating activities was net of contributions to employee pension plans of approximately $0.4 billion, $1.2 billion and $1.2 billion in 2014, 2013 and 2012, respectively. Cash provided by investing activities included proceeds and deposits related to asset sales of $5.7 billion in 2014, $1.1 billion in 2013, and $2.8 billion in 2012.

Restricted cash of $1.5 billion and $1.2 billion at December 31, 2014 and 2013, respectively, was held in cash and short-term marketable securities and recorded as “Deferred charges and other assets” on the Consolidated Balance Sheet. These amounts are generally associated with tax payments, upstream abandonment activities, funds held in escrow for asset acquisitions and capital investment projects.

Dividends Dividends paid to common stockholders were $7.9 billion in 2014, $7.5 billion in 2013 and $6.8 billion in 2012. In April 2014, the company increased its quarterly dividend by 7 percent to $1.07 per common share.

Debt and Capital Lease Obligations Total