Net Income  B. Liquidity and Capital Resources  Liquidity  85 The following table sets forth the summary of our cash flows for the periods indicated:  Our primary source of liquidity is cash flow from operations, which represents operating profit adjusted for non cash items,  primarily depreciation and amortization and changes in current assets and liabilities. We believe that our working capital is sufficient  to meet our present cash flow requirements.  In 2011, we generated NT$75.3 billion (US$2.5 billion) net cash from operating activities as compared to NT$84.8 billion  in 2010. The decrease was primarily due to a NT$6 billion (US$0.2 billion) decrease in cash flow from accounts receivable because  starting from 2011, we brought our billing period for monthly fees in line with that for connection charges, and due to a NT$2.3  billion (US$0.1 billion) decrease in income from operations owing to the increased operating cash outflow which outnumbered the  revenue in 2011. In 2010, we generated NT$84.8 billion net cash from operating activities as compared to NT$77.3 billion in 2009. The  increase was primarily due to a NT$4.1 billion increase in consolidated net income and the decrease in pension fund contribution  described below.  Historically, net cash from operating activities has been sufficient to cover our capital expenditures, including ongoing  expansion and modernization of our networks.  In 2011, net cash used in investing activities was NT$33.1 billion (US$1.1 billion), an increase from NT$17.4 billion in 2010.  The change was primarily due to the decrease in cash flow from disposal of available-for-sale financial instruments. In 2010, net cash used in investing activities was NT$17.4 billion, a decrease from NT$29.5 billion in 2009. The change was  primarily due to the increase in cash inflow from disposal of available-for-sale financial instruments.  In 2011, our net cash used in financing activities totaled NT$65.7 billion (US$2.2 billion), which mainly reflected NT$42.9  billion (US$1.4 billion) of payment of dividends during that period and NT$19.4 billion (US$0.6 billion) of cash distribution to our  stockholders for a capital reduction plan. P AR T I For the year ended December 31, 2009 2010 2011 NT$ NT$ NT$ US$ (in billions) Net cash provided by operating activities  77.3 84.8 75.3 2.5 Net cash used in investing activities  (29.5) (17.4) (33.1) (1.1) Net cash used in financing activities  (56.5) (47.0) (65.7) (2.2) Effect of exchange rate changes  — — 0.1 － Effect of change on consolidated subsidiaries 0.7 (2.8) (0.1) － Net increase (decrease) in cash and cash  equivalents  (8.0) 17.6 (23.5) (0.8) Cash and cash equivalents at end of year  73.3 90.9 67.4 2.2 As a result of the foregoing, our net income attributable to stockholders of the parent increased by 8.8% from NT$43.8 billion  in 2009 to NT$47.6 billion in 2010. Our net margin was 22.1% in 2009 and 23.5% in 2010. 