How many cell phones are there?

1) How many cell phones are there per person in the world?
1 or 2 for person aprox.
2) What are the differences in different countries? Can you comment some specific cases?
there are differences with all but the most opposite are Nigeria and Russia because Russia has the triple of phones than Nigeria.
3) What will happen in the future? R
All the persons will have a mobile phone and the most of them will have more than 1.
4) How is it that we can speak on a mobile phone without hearing other conversations from other people?
because the tecnology evolves so fast and some scientists have developed the technology to make no shock waves