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Faced with changing attitudes, tightening regulations and a booming online pornography industry, strip clubs are closing across the US. Sex may still sell in magazines and movies, but are American strip clubs a dying institution, asks Jonathan Berr.

"Can you imagine a boss telling a secretary to make an appointment at a strip club?"

These days, few executives would be willing to risk possibly losing their jobs and the resulting personal humiliation by seeking reimbursement from their employers for an outing at a strip club. But strip club operator Alan Markovitz said such calls were typical in the late 1980s and 1990s.

Mr Markovitz, a Michigan entrepreneur who has strip club operations in four states, told the BBC he would routinely get notified that a powerful executive was arriving to make sure that they got good seats.

"That was the norm back then," he said.

During the industry's heyday, customers weren't so timid. Strip club operators would even play along, using innocuous-sounding names on their credit card slips to avoid suspicion.

Indeed, strip club outings were tolerated on Wall Street and in other industries for years until female employees filed suit against their employers earlier in the decade and won tens of millions in lawsuits.

In addition, the industry is facing some punishing economic trends including a declining customer base, an abundance of free internet pornography and rising employee costs.

At live adult entertainment venues, selling sex it isn't nearly as profitable as it used to be.

Media playback is unsupported on your device Media caption Spearmint Rhino Strippers fighting for the right to strip

Data from market research group IBISWorld estimates profit slumped more than 12% to $1.4bn (£1.2bn) in 2018, down from $1.6bn in 2012. Sales during that same time period plunged about 7% to $6.9bn from $7.4bn.

Annual revenue growth at US strip clubs was 4.9% between 2012 and 2017, slowing to 1.9% from 2013 to 2018 and is projected to fall to 1.7% by 2023, according to IBISWorld.

The number of strip clubs has also declined in recent years in major US cities and their surrounding suburbs.

In New York City, tightening regulations may force more than half of the Big Apple's 20 joints out of business, according to the New York Post. The number of strip clubs in Atlanta has dropped from 45 to 30 in the last 10 years, according to Alan Begner, an attorney who represents strip clubs.

Some operators are being forced out by landlords while others are facing new bans on nude dancing in clubs which serve alcohol, where they get most of their profits, Mr Begner said.

Strip club owners are also facing federal class action lawsuit brought by dancers demanding to be classified as employees as opposed to independent contractors under the Federal Fair Labor Standards Act.

Image copyright Terraxplorer/Getty Images Image caption A sex shop in New York City

"That changes the game for a strip club operator," said Corey D. Silverstein, an attorney based in Bingham Hills, Michigan, who represents Mr Markovitz and other operators. "Now you are talking about having to comply with various state and federal employment laws. And on top of all of that having to pay benefits and (having to) treat all employees equally. It's a mess."

According to Crissa Parker, a stripper whose app called The Dancer's Resource allows dancers to warn others about conditions at clubs, performers also aren't benefiting from the increased legal protections and are seeing their incomes fall.

The changes add unwelcome stress for the many performers who hold other jobs like teaching and strip as a side job to make ends meet.

"You would never know that because they don't want to be judged due to the stigma," she said. "No one makes the same amount they made five years ago. The price of a dance has never changed. It's always been $20 regardless of the cost of living, house fees and whatever else you have got going on."

Strip clubs have also lost their cool among younger consumers. With some clubs stuck in the Mad Men era, young people are choosing to stay home where they have easy access to internet pornography.

"The Baby Boomers are retiring. They were for 20 years an amazing customer base," Mr Markovitz said. "The millennials are not coming to the strip clubs that much. That's the issue. "

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For one thing, many millennials can't afford to party at strip clubs. As CNBC noted, they have an average of $36,000 in personal debt excluding mortgages. Even those young consumers that can afford to patronize the clubs are taking a pass.

But it's probably not the nudity that is turning millennials off of strip joints.

A 2014 survey by women's magazine Cosmopolitan, found that 89% of respondents - who had an average age of 21 - had taken nude pictures of themselves. Only 14% said they regretted doing so.

However, Vice pointed out many millennial grooms feel uncomfortable being around strippers and would prefer to bond with their buddies over a game of laser tag or by organising trips.

Image copyright Michael Kovac/Getty Images for BET Image caption US rapper and Grammy winner Cardi B has been open about her past as a stripper

Kailin Moon, owner of New York's Rosewood Theater, a high-end gentlemen's club, argues that most adult entertainment venues have failed to keep up with the times. He prides himself in offering customers an experience lacking what he calls a "strip club vibe" without stripper poles. Performers are dressed in cocktail attire and are referred to as "atmospheric models."

But whatever the fate of strip clubs, pole dancing is showing its stamina.

Beyond the backlit interiors of strip joints, pole dancing has entered the mainstream, in the form of fitness classes.

"Pole dancing was this dirty little secret," said Devon Williams, the owner of Pole Pressure, a fitness studio in Washington, DC.

Now, "part of the stigma is going away", she said. "People want to get fit in alternative ways."

Pole Pressure offers 35 classes every week that emphasize both strength and body confidence. Ms Williams says the studio's Washington location guarantees a wide variety of clients: former strippers, lawyers, judges and babysitters.

"You can get any kind of person and they're just a person who loves the pole," she said.

And Ms Williams said she still gets calls every week from women recently hired as strippers, looking to improve their skills. For her, strip clubs may be on the decline but there is no shame around its signature dance.

"If someone were to call me a stripper I'd say thank you," Ms Williams said. "That means I'm confident and strong and it looks like I know what I'm doing."

"People are finding their best lives upside down."