The following table sets forth information regarding our mobile service operations and our mobile customer base for the  periods indicated.  Total mobile customers in Taiwan have reached approximately 29 million as of December 31, 2011. Mobile penetration was  approximately 124.3% on the same date. The overall mobile services market experienced a slight increase of 1.8% in revenues in  2011 mainly due to the growth in mobile data service as a result of our smart phone promotions.  We began offering prepaid card services in October 2000 and prepaid 3G card services in February 2008. As of December 31,  2011, we had approximately 1.1 million prepaid customers representing approximately 10.4% of our total mobile customers. Prepaid  customers do not pay monthly fees but pay a higher usage charge on a per second basis. Once the prepayment has been fully utilized,  a prepaid customer can make additional prepayments to continue the service. Alternatively, the customer may convert to become a  post-paid customer while retaining the same telephone number.  We offer incentives, such as mobile handset subsidies, when new customers agree to sign a service contract with us or when  existing customers renew their contracts with us ranging from 12 months to 30 months. We generally offer subsidies on mobile  handsets equipped with more advanced data functions to promote the expansion of our 3G mobile services. Smart phones accounted  for 48% of the total handsets we offered in 2011, and we expect that the percentage to reach more than 70% in 2012. We expect our  average subsidy per handset in 2012 will be less than that in 2011.  33 (7)  Average revenue per user per month is calculated by dividing our aggregate mobile services revenues during the relevant period  by the average of the number of our mobile customers on the first and last days of the period and dividing the result by the  number of months in the relevant period.  (6)  Average minutes of usage per user per month is calculated by dividing the total minutes of usage during the period by the  average of the number of our mobile customers on the first and last days of the period and dividing the result by the number of  months in the relevant period.  (5)  Measures the rate of customer disconnections from mobile service, determined by dividing (a) our aggregate voluntary and  involuntary deactivations (excluding deactivations due to customers switching from one of our mobile services to another)  during the relevant period by (b) the average number of customers during the period (calculated by averaging the number of  customers at the beginning of the period and the end of the period), and multiplying the result by the fraction where (c) the  numerator is 12 and (d) the denominator is the number of months in that period.  (4)  Includes GSM, GPRS and 3G services.  (3)  Data from the statistical monthly release by the National Communications Commission in the Republic of China, which include  mobile revenues 2G, 3G and PHS.  (2)  The number of mobile customers is based on the number of subscriber identification module, or SIM, cards. Since 2006, the  total number of mobile customers in Taiwan included personal handy-phone system, PHS and 3G customers.  (1)  Data from the Department of Population, Ministry of the Interior, Republic of China  P AR T I As of or for the year ended December 31, 2009 2010 2011 Taiwan population (in thousands) (1) 23,120 23,162 23,225 Total mobile customers in Taiwan (in thousands) (2) 26,959 27,840 28,862 Penetration (as a percentage of the population) (2) 116.6% 120.2% 124.3% Total mobile revenues in Taiwan (in billions) (3) NT$  215.2 NT$  213.2 NT$  217.0 Number of our mobile customers (in thousands) (2)(4) 9,269 9,679 10,072 Our market share by customers 34.4% 34.8% 34.9% Our market share by revenues 33.1% 34.2% 32.6% Number of our prepaid customers (in thousands) (4) 839 945 1,052 Our prepaid customers as a percentage of our total customers 9.0% 9.8% 10.4% Annualized churn rate (5) 11.21% 10.35% 11.52% Minutes of usage (in millions of minutes) Incoming 10,500 11,063 11,368 Outgoing 9,702 10,190 10,897 Average minutes of usage per user per month (2)(6) 185 187 188 Average revenue per user per month (2)(7) NT$ 653 NT$ 643 NT$  598