I enclose this graph which states the position as of 2006/2007, so this is reasonably up to date.
There are a few things to bear in mind here.
1. 'Other Religions' genuinely includes all other religious persuasions, everything from Judaism (the biggest single group here) to such religions as Sikhism, and on to Confuscianists in the Far East. But numerous groups - often very small - are included here.
2. The 'Non-religious' group are not necessarily all atheists, in fact, far from it: It has previously been estimated that there are fewer than 2% commited atheists in the world! Rather, these are people who would not describe themselves as "religious" yet many may - and often do - believe in some concept of 'God,' but probably not the Divine, Almighty God of Theism in many cases.
3. Of the estimated 2006/2007 world population of 6.5 billion people, 2.1 billion people call themselves 'Christian' (whether Roman Catholic, Protestant, Anglican, Eastern Orthodox or whatever else). But many of these people are only talking about tradition, not about personal, deeply-held belief. so liberal Christians are necessarily included here. Moreover, this grouping includes the many sub-Christian sects such as the Mormons, Jehovah's Witnesses, Seventh Day Adventists etc., whom most Christians would not regard as "fellow Christians." Nevertheless, it could be claimed that 'Christians' (in an admittedly very loose sense), make up about 33% of the world population; without doubt, that is an impressive figure!
4. Although conversions to Christianity keep pace with the growth in world population (a very encouraging fact in it's own right), more worryingly, conversions to Islam now outstrip the growth in world population (note figures given directly beneath the chart).
Robin A. Brace, January 1st, 2009.