and 2013, respectively. Income tax expense as a percentage of income before taxes, or our annual effective tax rate, was 16.5%, 13.8%, and 15.0% in fiscal years 2015, 2014 and 2013, respectively. The difference in the effective tax rates amongst the three years was primarily due to an increase in the amount of earnings subject to United States tax in fiscal year 2015 and a higher percentage of research tax credit benefit in fiscal year 2014.



Our effective tax rate on income before tax for the fiscal years was lower than the United States federal statutory rate of 35% due to income earned in jurisdictions, including British Virgin Islands, Hong Kong, China, Taiwan and United Kingdom, where the tax rate is lower, favorable recognition of the U.S. federal research tax credit and release of tax reserves as a result of the expiration of statutes of limitations in certain non-U.S. jurisdictions for which we had not previously recognized related tax benefits.



Please refer to Note 13 of the Notes to the Consolidated Financial Statements in Part IV, Item 15 of this Annual Report on Form 10-K for additional information.



Liquidity and Capital Resources 

 

As of January 25, 2015, we had $4.62 billion in cash, cash equivalents and marketable securities, a decrease of $48.5 million from the end of fiscal year 2014. Our portfolio of cash equivalents and marketable securities is managed on our behalf by several financial institutions which are required to follow our investment policy, which requires the purchase of high grade investment securities, the diversification of asset types and includes certain limits on our portfolio duration.

  

Cash provided by operating activities increased in fiscal year 2015 compared to fiscal year 2014 primarily due to higher net income from revenue growth and contained operating expenses, partially offset by an increase in inventories resulting from the introduction of newly launched Maxwell-based GPUs and certain Tegra SOCs and SHIELD devices, and an increase in accounts receivable. Cash provided by operating activities increased slightly in fiscal year 2014 compared to fiscal year 2013 primarily due to a decrease in operating assets offset by a decrease in net income. The decrease in operating assets was driven mainly by a combination of a decrease in accounts receivable, resulting from strong collections and linear monthly shipments in the fourth quarter of fiscal year 2014, and a decrease in inventories.



Cash used in investing activities for fiscal year 2015 decreased from fiscal year 2014 primarily due to lower purchases of property and equipment and intangible assets. Cash used in investing activities for fiscal year 2014 increased from fiscal year 2013 driven primarily by capital expenditures in fiscal year 2014 for new technology licenses and leasehold improvements at our facilities in various locations.



Cash used in financing activities in fiscal year 2015 resulted primarily from our repurchase of $813.6 million of shares of our common stock and our cash dividend payments totaling $186.5 million. These uses of cash were offset by cash proceeds of $153.5 million from common stock issued under our