The chart shows the number of fixed (main) telephone lines in the world, including the historical data (blue dots) from the International Telecommunications Union (ITU) for the period 1960-2008 and from other identified sources for the period previous to ITU's coverage, and areppim forecast until 2025 (red S-shaped line). The horizontal yellow line represents the technological ceiling hit by the fixed line telephony in 2006-2007.

According to the forecast model, the total number of telephone lines might hit the saturation volume of 3.6 billion in the second half of the 21st century, reaching the inflexion point by 2019. Reality is quite different. The mobile phone revolution has already disrupted that growth trend and "killed" the prosperous life of the fixed lines. Some landmarks are:

• 2001: cellular technology substitutes to fixed line telephony.
• 2006: the growth of fixed lines is stopped and reversed. The "normal" life-cycle of the fixed line technology is curtailed by the winning competitive cellular technology.
• The growth has been exponential until 1999, when the volume reached 904 million lines. After this inflexion point, growth started to decelerate reaching the technological plateau in 2006-2007 and starting the fall thereafter. The available data points do not allow as yet to estimate the falling speed and the bottom level to be reached.

The history of telecommunication technologies offers other instances of thriving products whose life has been brutally shortened by an aggressive newcomer. It happened with Morse telegraph, telex, telefax, mail. Acknowledging this is a sobering exercise for whomever is conceited enough to believe that forecasting can foresee the future — it only suggests a possible scenario, given how much one really knows about the past (incomplete series) and the unknowns about the present (disruption factors).

The forecast uses a logistic growth function based on historical data, two key parameters being a slope coefficient calculated by the least squares procedure and a saturation point estimated by bootstrapping. The quality of the available statistical series determines the robustness. Telephone has been invented in the 19th century, but information about the number of existing lines covers only the period 1900 onwards and even so in a very incomplete way until 1975.

Sources: ITU International Telecommunications Union for the period 1960-2008, and Huurdeman, A. (2003) The Worldwide History of Telecommunications, Hoboken NJ, John Wiley & Sons, for data previous to 1960.

  areppim: information, pure and simple