Last week, Boston Mayor Martin Walsh asked the City Council to allow him to waive the residency requirements 75 to 100 of his top officials.

City officials, like most city employees, are required by law to live in the city. But the pushback was swift from councilors like Tito Jackson and Michelle Wu and citizens groups like Save Our City, and this week, Walsh quickly backed away from the fight, and pulled his request from consideration.

To understand why most Boston city employees are required to live in the city, we’ll have to take a quick jaunt in the way-back machine, to the era of loud prints, high gas prices and urban flight.

"Across America, cities saw enormous exodus of middle class people," said former city councilor Lawrence DiCara, who helped draft the legislation that established residency rules for city employees. "Boston lost probably 10 percent of its population from the early 1970s until '76 or '77."

Cities across the country needed to stop the bleeding. One strategy: Require at least city employees to stay in the city.

"Going forward, we needed to ensure that those solid middle class folks who worked in the city lived in the city," DiCara said.

When the U.S. Supreme Court affirmed the legality of residency requirements in 1976, cities from Detroit to Denver to Cincinnati to Chicago jumped on the bandwagon. Boston did too. According to the Walsh administration, by 1980, two-thirds of the country’s large cities had residency requirements.

But what about today? After all, urban flight is as long-gone as Studio 54. In fact, most American cities — Boston included — have been growing for years. So are residency requirements still the norm?

In America’s largest cities, they are. In New York, it’s a bit of a mixed bag. Some employees must live in the city; others can also live in one of the six surrounding counties. In LA, city workers can live wherever they want, but in Chicago, the city still holds a firm grip. If you want to work for the Windy City, you have to live in the Windy City.

But despite its outsized influence, Boston is not one of America’s largest cities. And when you compare Boston to more similarly-sized cities, you find that we’re a bit of an outlier these days.

Seattle has never had a residency requirement. Denver and Baltimore did away with theirs years ago. In San Francisco, which like Boston, is both bullish on the innovation sector and one of the most expensive cities in America, there’s no residency requirement either.

DiCara points out that the requirements here today are not quite as strict as they used to be, largely because of longstanding opposition from unions.

"Through the years, however, through the collective bargaining process, some of the residency issues were bargained away at the table," he said. "There also have been some state laws, especially relating to police and fire, which trump the city ordinance."

For example, teachers and principles can now live anywhere. But school custodians and school police still have to live in town for at least 10 years. All told, around a third of the city’s roughly 18,000 full-time employees live outside the city.

Now there’s no shortage of arguments for and against the policy. Some are economic, others philosophical. But perhaps the real question is whether it’s time to once again have the debate. DiCara, for one, says that it most certainly is.

"I think as a matter of policy, anything we voted upon in the '70s should be looked at," he said. "Regulation of cabs, hours of operation of licensed establishments, you name it. Everything should be on the table, including this."

But with Mayor Walsh so quickly withdrawing his request this week for the authority to waive the residency requirement for some of his top officials, it doesn’t look like that will be happening anytime soon.