Once upon a time, back in the middle of the 20th century, the smallest theater on Broadway could have comfortably accommodated a get-together of all the New Yorkers worth at least $100 million. Not anymore. Broadway’s landmark Helen Hayes Theater holds a mere 597 seats. The number of “centi-millionaires” who currently call the City of New York home: 744.

New York currently hosts, researchers at the London-based Henley & Partners have just reported, more centi-millionaires than any other city on Earth. And if hosting centi-millionaires ever became an Olympic sport, the Henley stats show, the USA would be bringing home gold, silver, and bronze.

The San Francisco Bay Area — now teeming with 675 centi-millionaires — rates as the world’s second-most-popular home to fortunes worth over $100 million. Los Angeles sits third with 496.

Our world’s most stout defenders of grand fortunes, for their part, find these stats a mite inconvenient.

Why this unease? The presence of all these super rich in New York, the Bay Area, and Los Angeles undercuts a key claim of our don’t-tax-the-rich set. That claim: If confronted with any substantial tax rate, people of major means will simply pack up and relocate in places that better appreciate how selflessly noble deep pockets can be.

In other words, claim friends of grand fortune, lawmakers inclined to significantly tax the rich are playing a foolish game they cannot possibly win. But the rich who live in New York, San Francisco, and Los Angeles all face state and local taxes considerably higher than the rich who live in most all other major metropolitan areas. Yet these rich haven’t yet picked up and moved elsewhere.

Norway has become just the latest political jurisdiction to go through a don’t-dare-tax-the-rich debate. Norway’s current Labor Party-backed government has proposed expanding an existing “exit tax” on the nation’s rich who choose to emigrate. These rich, if this change goes through, will start owing taxes on any substantial capital gains they haven’t yet realized before their exit.

This move has horrified cheerleaders for Norway’s deepest pockets. The Norwegian Alliance for Startup and Tech, a high-tech lobby group, says this added tax liability is going to make it “a lot harder” for Norway to attract talent and capital.

Norway’s super-rich, the Alliance believes, “will flee to Switzerland” to avoid the new exit levy.

Mark Thomas, a British business consultant and business school prof, would beg to differ. The author of The Complete CEO and 99%, Thomas last week dealt the standard case for not taxing the rich a convincing counter.

Yes, Thomas acknowledges, some rich have indeed exited their home societies in search of greener lower-tax pastures. The holder of Britain’s biggest private fortune, the billionaire Jim Radcliffe, did move to tax-haven Monaco to avoid the equivalent of over $5 billion in taxes. But no parade of Britain’s rich has followed in Radcliffe’s path. Year in and year out, London continues to rate as one of the world’s best places to live for people of means. Monaco doesn’t appear in the top 100.

“If you care about quality of life,” notes Thomas, swapping London for Monaco “makes no sense.”

What about the argument that nations with taxes high enough to drive their rich away will lose out on the investments these rich would be making if they stayed home? If these nations “print” more money to make up for those lost investments, this argument continues, they’ll simply unleash horrible inflation.

Governments, of course, print money all the time. But they can’t, Thomas notes, “print” construction workers or doctors and nurses. If we want to devote more resources to better housing and health care, “we must free up real resources from less vital tasks” — like the luxuries the rich so crave. Those nonessential luxuries consume the resources “needed to deliver things that are essential for society.”

“We should not be afraid of any exodus” of the rich, Thomas concludes. “We should simply shrug” at that prospect.

“Penalizing” the rich with high tax rates, the rich people-friendly counter, will only end up leaving economies sputtering and everyone in them worse off. High taxes, they insist, mean low economic growth. But America’s best economic years over the last century, Thomas points out, have come when the United States was taxing the nation’s highest income brackets at rates over 80 percent.

“If anything,” Thomas adds, “the evidence suggests that tax cuts hurt the economy — because they prevent the government from investing in the future and helping those who need it most.”

Fans of grand fortune have always struggled to refute that evidence. In the end, sooner or later, they find themselves parroting some version of the oldest rationale for letting the riches of the rich just be. Our richest, this rationale goes, deserve their good fortune. Their brilliance entitles them to it.

One certifiably brilliant billionaire, James Simons, just happened to kick the bucket earlier this month at age 86. This award-winning mathematician helped forge breakthrough in fields ranging from autism to the origins of the universe. He also just happened to launch the hedge fund that would become “one of the most profitable investment firms in history.”

But Simons had little patience for those who ascribed his mega-billion fortune to his brilliance.

“One can predict the course of a comet more easily than one can predict the course of Citigroup’s stock,” he noted at one point. At another: “In this business it’s easy to confuse luck with brains.”

“Luck is largely responsible for my reputation for genius,” Simons summed up at still another moment. “I don’t walk into the office in the morning and say, ‘Am I smart today?’ I walk in and wonder, ‘Am I lucky today?’”

Simons, as perceptive as he could be, never quite understood that entire societies can actually change their luck. They can work to become more equal.