Many Mobile apps now offer either voice messaging (Wechat) or straight VoIP functionality (Skype, Viber, Line). While it is difficult to prove a direct linkage between usage of these apps and usage/revenue trends within the traditional telcos, there is at least anecdotal evidence that, on average, rising 3G / 4G penetration rates are usually associated with falling voice minutes of use.
We do not attempt to prove that messaging apps are cannibalizing voice. Instead, we attempt to quantify the cost savings to users (and therefore the voice revenue risk to operators) were subscribers to move their current voice usage over to a VoIP data based pricing model.
Compression ratios for the various CODECs used by VoIP providers vary, but we understand the most frequently used is the G.729 CODEC. Adjusting a minute