9 Capitalized contract costs

As of December 31, 2019, the carrying amount of capitalized contract costs stood at EUR 2.1 billion and was thus EUR 0.3 billion higher than at the end of the prior year. This increase is attributable in particular to a higher level of capitalized costs of obtaining a contract in postpaid customer business in the United States operating segment as of the end of the reporting year. The costs of obtaining a contract primarily contained sales commissions paid to third-party retailers in the direct and indirect sales channel and to employees. Overall, capitalized contract costs of EUR 1,388 million (2018: EUR 976 million) were written down on a straight-line basis over the estimated customer retention period.