Belial,

I suspect that it is because the people who prepare the images believe that it helps sales. While interracial pairing is no longer illegal or taboo, it is still, for many, titillating. Titillating sells.

I don’t mean that in a deprecating way. As LixyChick pointed out in her post, the ratio seems to her to be reversed in television shows. Look at it from the point of the Producer/Director/Script Writer. By introducing an interracial pairing into a plot, many social interactions and complexities can be explored. Such explorations can enliven an otherwise dull product, drawing the attention which advertisers crave and pay for.

Assuming that your perceptions do correctly reflect the actual ratios in your viewing area, and are not a comment about what catches your attention (you must admit that possibility), then why which ratio predominates in a particular genre may depend upon the statement being made in the production.

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Eudaimonia