Final answer:
As of 2009, there were approximately 4 billion mobile phone users worldwide. This number sets a precedent for an increased count in 2015, but the exact figure for that year is not provided. Companies have been investing in shared-phone programs to capitalize on this widespread mobile connectivity.
Step-by-step explanation:
The student has asked how many mobile phone subscriptions there were in the world in 2015. According to the International Telecommunication Union's report "The World in 2014: ICT Facts and Figures," there were approximately 4 billion mobile phone users worldwide by 2009. While this information does not directly provide the number for 2015, it is indicative of substantial global mobile phone penetration, potentially setting the stage for even higher numbers in the years following, taking into account the upward trend in mobile phone usage and subscriptions. Companies like Vodafone and Masbabi have funded shared-phone programs aiming to increase market share and provide innovative tools in peripheral nations!