PHILADELPHIA (CBS) – Add this to the list of reasons you should be getting more sleep. Researchers say more sleep may mean more money in your pocket.

Studies have found that a good night of sleep sparks productivity and efficiency, which in the end helps you earn more money.

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According to MarketWatch, the research is from a paper by Williams College’s Matthew Gibson and Jeffrey Shrader from the University of California at San Diego.

Gibson writes, “After about seven days during which people sleep six hours a night, they perform almost as badly on tasks as someone deprived of sleep one night.”

Gibson and Shrader found what time the sun goes down may affect how well a person sleeps, and therefore may affect their earnings.

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For example, people who live in locations with higher hours of sleep, such as Huntsville, Ala., earn 5 percent more than people in locations with an hour less of sleep, such as Amarillo, Texas.

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The paper says the two cities are in the same time zone, but had different sunset times.

Gibson says,“Our own subjective impairment of sleep may not be a good guide on how we are doing on the job,” he said

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The National Sleep Foundation recommends adults 18 to 64 years old should be getting seven to nine hours of sleep per night.