Mara Hvistendahl’s in her book: Unnatural Selection: Choosing Boys Over Girls, and the Consequences of a World Full of Men, reports ".... a sobering update on the gender imbalance that is growing ever-more prevalent around the world, but especially in Asia. As a result of sex-selective abortion by families desiring boys, India has a ratio of 112 boys for every 100 girls; in China it’s 121 to 100. (The “natural” sex ratio is 105 to 100 and biologists consider anything over 106 to be "impossible.") With the passage of time and continued population control measures in, especially, India and China, she puts the number of “missing” women at more than 160 million. The number is so high as to be practically incomprehensible, but Hvistendahl puts it in perspective: It’s more than the entire female population of the U.S..."
(quoted from: http://www.slate.com/blogs/xx_factor/2011/07/08/unnatural_selection_by_mara_hvistendahl_is_the_doublex_book_of_t.html)