Income from operations and Operating Margin  As a result of the foregoing, our income from operations increased by 1.7% from NT$56.4 billion in 2009 to NT$57.4 billion  in 2010. Our operating margin decreased from 28.5% in 2009 to 28.3% in 2010.  The following table sets forth certain information regarding our operating income by business segment for the periods  indicated.  As a result of the foregoing, segment income before tax for our domestic fixed communications business increased by 3.4%  from NT$17.4 billion in 2009 to NT$18.1 billion in 2010; segment income before tax for our mobile communications business  decreased by 2.8% from NT$30.2 billion in 2009 to NT$29.3 billion in 2010; segment income before tax for our internet business  increased by 5.1% from NT$9.3 billion in 2009 to NT$9.8 billion in 2010; segment income before tax for our international fixed  communications business increased by 4.0% from NT$2.6 billion in 2009 to NT$2.7 billion in 2010; and segment loss for our others  business segment decreased by 5.5% from NT$2.3 billion to NT$2.2 billion.  Our other income, net decreased by 62.1% from NT$0.8 billion in 2009 to NT$0.3 billion in 2010. This decrease was  primarily to a NT$0.2 billion loss on disposal of property, plant, and equipment, and a NT$0.1 billion net loss on valuation and  disposal of financial instruments, and a NT$0.1 billion net loss on foreign exchange.  Other Income, Net  Income Tax  Our income tax was NT$12.7 billion in 2009, compared to NT$9.1 billion in 2010. Our effective tax rate was 22.3% in 2009  and 15.8% in 2010, primarily due to the reduction of the corporate income tax rate in the R.O.C. from 25% to 17% effective from  2010. Please refer to “Item 5. Operating and Financial Review and Prospects—Taxation” for a discussion of the change in tax rate.  P AR T I Domestic Fixed  Communications Mobile  Communications Internet International  Fixed  Communications Others Adjustment Total (in billions of NT$) For the year ended  December 31, 2010 Revenues from external  customers  70.7 89.0 24.5 15.5 2.7 — 202.4 Intersegment service  revenues  14.7 2.1 1.1 1.7 0.7  (20.3) — Interest income  — — — — 0.5 — 0.5 Other income  0.3 0.1 0.3 (0.2) 85.4 91.4 25.6 17.3 4.2 (20.5) 203.4 Segment income before  tax  18.1 29.3 9.8 2.7 (2.2) — 57.7 For the year ended  December 31, 2009 Revenues from external  customers  71.5 86.5 23.7 15.2 1.5 — 198.4 Intersegment service  revenues  13.7 1.9 0.7 1.5 — (17.8) — Interest income  — — — — 0.5 — 0.5 Other income  0.1 0.1 0.7 0.9 85.2 88.5 24.5 16.7 2.7 (17.8) 199.8 Segment income before  tax  17.4 30.2 9.3 2.6 (2.3) — 57.2 84