India has 37 million more men than women, partly because the preference for sons prompts sex-selective abortions and infanticide.

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However, because there is such a strong contrast in the preference for menthol by race and sex and because there are large differences in the rates of these cancers also by race and sex, we felt that this was a case in which an ecologic approach could be informative.

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The other reason specific to a few Asian societies is because a combination of traditional preference for sons and the availability of sex-selective abortion skewed the sex ratio at birth 20 years ago, leaving too few native-born women now.

ECONOMIST: International marriage