Imported from Europe, the custom of leaving gratuities began spreading in the U.S. post-Civil War. It was loathed as a master-serf custom that degraded America's democratic, anti-aristocratic ethic. Hulton Archive/Getty Images hide caption

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At fine-dining places, white workers overwhelmingly fill jobs with the heftiest salaries, while Latinos, blacks and other minorities have jobs with pay closer to the poverty level, a study finds. iStockphoto hide caption

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Staff in the kitchen of The Modern, a restaurant operated by Meyer's Union Square Hospitality Group and located in the Museum of Modern Art. Ellen Silverman/Union Square Hospitality Group hide caption

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Diners fill Riverpark, a New York City restaurant, in January. Restaurateurs fear that the tipped-wage hike being proposed in New York will force them to get rid of tipping altogether. Brad Barket/Getty Images hide caption

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Figuring out how much to tip, and when, is a delicate science. Some businesses are integrating technology into how you pay to encourage you to tip more. Dan Bobkoff/NPR hide caption

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