In India and China, sex-selective abortion has skewed the gender ratio by 10-20% in either country with females being aborted at a much higher rate. In addition, this type of gender imbalance is beginning to crop up in unexpected places, including parts of the world where there had been no history of sex-selective abortions. Niemen Watchdog has a detailed piece on this topic here. Here's an excerpt:
Results from the Indian and Chinese censuses released earlier this year show the sex ratio at birth becoming more skewed in both countries. China counted fully 118 boys born for every 100 girls, while India, which uses an alternative statistic, reported 914 girls for every 1,000 boys, ages 0-6. (The natural human sex ratio at birth, by contrast, is 105 boys per 100 girls.) Sex selection, mainly through abortion, has been practiced on a broad scale in South and East Asia since the early 1980s, when cheap ultrasound machines able to detect the sex of a fetus in the second trimester were first marketed in China, India, South Korea, and Taiwan. If Asia's sex ratio at birth had remained at its natural equilibrium over the past few decades, one demographer found in 2005, the continent would have an additional 163 million women and girls today.Equally alarming is the fact that sex selection is spreading. In the past fifteen years, skewed sex ratios have cropped up in countries with no history of the problem – including Vietnam, Georgia, Azerbaijan, Armenia, and Albania. Sex selection also occurs in the United States.That more boys than girls are born is now widely accepted, as is the fact that gender imbalance on the scale of Asia's has serious societal implications. As millions of what demographers call “surplus males” grow up and cannot find wives, they are turning to poorer countries to buy them. Asia's sex ratio imbalance has also contributed to an increase in sex trafficking.