P AR T I 75 Each of our operating segments is managed separately because each represents a strategic business unit that serves a different  market. We measure our segment performances mainly based on revenues and income before tax.  Due to the change in policy for collecting the tariffs for fixed line-to-mobile calls starting from 2011 as discussed in “Domestic  Fixed Communications Business”, “Interconnection” and “Regulation—Interconnection Arrangements” of “Item 4. Information on  the Company—B. Business Overview”, our domestic fixed communications revenues and cost of revenues increased in 2011, while  mobile communications revenues for the same period decreased.  The following table sets forth our revenues, operating costs and expenses, income from operations and other financial data as  a percentage of our total revenues for the periods indicated.  For the year ended December 31, 2009 2010 2011 (as percentages of total revenues) Revenues: Domestic fixed communications 36.0% 34.9% 36.5% Mobile communications 43.6 44.0 42.8 Internet 11.9 12.1 11.4 International fixed communications 7.7 7.7 7.0 Others 0.7 1.3 2.3 Total revenues 100.0% 100.0% 100% Operating costs and expenses: Operating costs 56.8% 57.0% 60.5% Operating expenses: Marketing 11.2 11.1 10.7 General and administrative 1.9 2.0 1.9 Research and development 1.6 1.6 1.6 Total operating costs and expenses 71.5 71.7 74.7 Income from operations 28.5 28.3 25.3 Other income, net 0.4 0.2 0.8 Income before income tax expense 28.9 28.5 26.1 Income tax expense 6.4 4.5 4.0 Consolidated net income 22.5% 24.0% 22.1% Attributable to: Stockholders of the parent 22.1 23.5 21.6 Minority interests 0.4 0.5 0.5  For the year ended December 31, 2009 2010 2011 NT$ NT$ NT$ US$ (in billions) Revenues: Domestic fixed communications 71.5 70.7 79.4 2.6 Mobile communications 86.5 89.0 93.0 3.1 Internet 23.7 24.5 24.8 0.8 International fixed communications 15.2 15.5 15.2 0.5 Others 1.5 2.7 5.1 0.2 Net revenues 198.4 202.4 217.5 7.2 Operating costs and expenses: Operating costs 112.7 115.3 131.5 4.4 Operating expenses: Marketing 22.3 22.5 23.2 0.8 General and administrative 3.8 4.0 4.2 0.1 Research and development 3.2 3.2 3.5 0.1 Total operating costs and expenses 142.0 145.0 162.4 5.4 Income from operations 56.4 57.4 55.1 1.8 Other income, net 0.8 0.3 1.6 0.1 Income before income tax expense 57.2 57.7 56.7 1.9 Income tax expense 12.7 9.1 8.6 0.3 Consolidated net income 44.5 48.6 48.1 1.6 Attributable to: Stockholders of the parent 43.8 47.6 47.1 1.6 Minority interests 0.7 1.0 1.0 -