I don't think it's possible to accurately answer that question. \nSome countries may not even know themselves how many of their own people have gone missing, or even worse, mis-represent how many have gone missing due to the efforts of secret-police type organisations.\n\nIn some cases it's up to 3rd parties like the Red Cross to give numbers on thing like this, see:\nhttp://www.redcross.org/news/in/africa/020130lagos.html\nhttp://www.redcross.org/press/intl/in_pr/010412kosovobook.html\nfor example.
How many people go missing every year world wide?