After emerging from the crisis of 2000, the telecommunication industry is being transformed. Technological changes and the development of new services are affecting the core businesses of telecommunication operators. Voice continues to be the key driver in OECD telecommunication markets which have now attained revenues of USD 1 trillion. However, voice services, and the structure of telecommunication revenues, are evolving. Mobile services now make up 40% of all OECDarea telecommunication revenues, and mobile subscribers outnumber fixed subscribers by a ratio of 3 to 1. At the same time, technologies such as Voice over Internet Protocol (VoIP) are exerting strong downward pressure on prices for voice services. The impact of VoIP is apparent in prices for international fixed-line calls, which many VoIP operators now bundle into flat-rate subscription plans. As a result, the future of voice revenue streams is unclear.