Do people like happy endings? Yes:
Forty-one per cent [of respondents] are overwhelmingly in favour of books with a happy ending, as against 2.2% who like it sad. Women were 13% more likely than men to say they want it all to end happily. Almost one fifth of men expressed a preference for books with ambiguous endings.
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Young people were most likely to prefer books with a sad ending – 8.6% of under 16s. Those aged 41-65, however, a group with more personal experience of sadness, dislike sad endings, with only 1.1% preferring books that end this way.
Those numbers come from the World Book Day website survey, so they’re not exactly scientific, but they certainly do match common wisdom.