This week, the Marriott hotel chain announced a partnership with former California First Lady Maria Shriver in a new campaign called The Envelope Please. The campaign encourages Marriott guests to tip cleaning staff by providing envelopes in which to deposit a few bills.

For those who assume damp towels, heaping garbage and Funyuns-encrusted bedsheets magically clean themselves, The Envelope Please is a way to give the workers — many of whom are women — their due above and beyond hourly wages.

The average maid or housekeeper in 2012 made  $9.51 per hour, or just under $20,000 in annual salary. For many workers that's simply not enough to sustain themselves, let alone their families.

Harvard Business School historian Nancy Koehn appeared on Boston Public Radio to look at whether Marriott International, Inc. — and Maria Shriver, by extension — are passing the burden of worker compensation onto consumers.

"They have roughly 20,000 housekeepers. They're almost all women, most of them aren't living in expensive zip codes," Koehn said of Marriott and its housekeepers. "Why don't we just pay them more?"

Koehn explained that housekeepers are often an afterthought in the tipping economy. Most people think, "'Well, I've tipped the bell person, I tipped the waiter or the waitress at the restaurant, I came in in a taxi and I gave the taxi driver a tip.' You don't always think that there's a whole bunch of other people that may be worthy of a tip — people who clean your room," Koehn said. "The envelope will remind you."

Boston Public Radio cohost Margery Eagan said precedent plays a role in tipping practices. "One of the reasons waiters and waitresses get good tips is because everybody knows you're supposed to tip waiters and waitresses. Most people don't know" to tip housekeepers and maids, Eagan said.

"Tipping as we understand it most likely originated in what we might call the Early Modern period, make it 1500, 1600," Koehn said. "Travelers carried money to tip highwaymen not to rob them! (...) That became part of a wider tributary — if you will — of money flowing in which aristocrats would tip. It was called "giving the vails," giv[ing] coins, to the servants of the house in which they stayed. (...)

"By the late 19th century, the late 1800s, [writer] Samuel Johnson reportedly drank coffee at Fleet Street (...) and there were supposedly bowls put on tables that said 'to insure prompt service' or 'to insure promptitude.' And that morphed into 'tips.'

"By the beginning of the Industrial Revolution (...) some of the aristocratic rural life was morphing into a more urban life, and guess what? All the newly-emerged middling classes (...) began tipping in cities," Koehn explained. "That process came to America in the decade or two after the Civil War."

Despite its long historical roots, what would happen if the subjective practice of tipping were done away with? Boston Public Radio cohost Jim Braude summarized the main argument against that idea. "There's no incentive for an average worker — who is traditionally a tipped worker — to treat you decently," Braude said.

But Cornell University professor Michael Lynn debunked that theory in his study,  Tipping and Service Quality[PDF]. Lynn noted our perceptions of service are highly subjective, and beyond that, there is a great "variability" in the cash rewards — tips — we're compelled to leave. 

So, if the customer isn't a reliable barometer for service quality, there's a good chance, from time to time, that a server or housekeeper will get under-tipped, or completely stiffed. Service workers know the scenario all too well. In the end, it may only be the employer — with a keen feeling for morale and a sense of decency — who can keep workers at a consistent, livable wage.