Income inequality has company — make that companies. A new wealth gap is opening among U.S. corporations, where cash holdings are growing more concentrated as the rich get richer.

Eighteen American businesses held 36 percent of corporate wealth in 2013, up from 27 percent in 2009, according to a report from Standard & Poor’s, a credit rating firm in New York. The bottom 80 percent have lost ground, with just 11 percent.

The top 1 percent is a Who’s Who of multinationals, including Microsoft Corp., Google Inc., Coca-Cola Co., Apple Inc. and Ford Motor Co., that reap a big share of profits from non-U.S. sales.

Because tax law discourages moving that money back to the U.S., cash is piling up abroad and companies are taking novel steps to adapt, including borrowing against those assets to finance operations at home.

“Unlike individuals, corporations don’t want to be in that top 1 percent,” said analyst Andrew Chang, lead author of the S&P report. “This rising cash balance among the richest is tax- policy driven.”

American multinationals are taxed by the country where profits are earned and by the U.S. when — or if — the money is brought back. The corporate tax rate in the U.S., running up to 35 percent, is the highest in the industrialized world.

Companies have long lobbied Congress to rewrite the code as cash for the wealthiest 1 percent rose to 23.6 percent as a share of total assets last year from 20.4 percent in 2009, Chang found. For everyone else, it accounted for less than 7 percent.

More Accumulation

“Overseas cash continues to accumulate without being touched,” Chang said. “It’s undoubtedly going to increase.”

That’s bad for investors, who like to see money put to use or returned to shareholders. It’s also not good for the deficit-ridden Treasury, which missed out on an estimated $83.4 billion in tax revenue this fiscal year as companies delay bringing back earnings, according to the congressional Joint Committee on Taxation.

And it can’t buy happiness for one-percenters such as Medtronic Inc. that are taking drastic steps to make use of their earnings overseas. The medical-device manufacturer is taking some $13 billion it has offshore to buy a London-based competitor in an inversion, a merger which enables it to move headquarters abroad and pay lower taxes.

“Obviously we’d rather have our cash work for us because it’s sitting in accounts with low interest rates and there’d be better ways to invest that money,” said Fernando Vivanco, a spokesman for Medtronic. “Are there any companies that you know that could say we love having our cash trapped?”

Domestic Assets

While Chang estimated 83 percent of cash held by the wealthiest 1 percent comes from foreign earnings, domestic assets are shrinking to the point that there’s not always enough to finance U.S. operations, he said.

That’s one reason Apple, Cisco Systems Inc. and other one- percenters are borrowing. Cupertino, California-based Apple, which has 78 percent of its $40.7 billion overseas, caused a stir last year when it said it would take on $17 billion in debt to make dividend payments. The company went back to the bond market in April.

It’s cheaper to borrow against foreign cash than repatriate it, Cisco spokesman John Earnhardt said. Ninety-three percent of the San Jose, California-based Cisco’s $47.1 billion is held outside the U.S.

“If a territorial tax were instituted or an acceptable level of corporate tax was instituted, we’d bring that money back,” Earnhardt said. “Would it be better utilized here, where our corporate headquarters is? Yes.”

Weighing Inversions

While that borrowing has kept money circulating in the U.S. economy, it’s a holding pattern that can’t be sustained if interest rates rise and prospects for tax legislation dim. That’s why more executives are weighing mergers with foreign companies in order to lower taxes, said Douglas Holtz-Eakin, an unpaid adviser to the Alliance for Competitive Taxation, a Washington business group lobbying for tax reform.

“They’ve given up, they think there’s no hope,” said Holtz-Eakin, an economic adviser to former President George W. Bush. “And when the headquarters go, they’re likely to put R&D next to the headquarters.”

When Minneapolis-based Medtronic completes its merger with Covidien Plc, it will get an Irish address and put future earnings out of reach of U.S. tax collectors.

In May, London-based AstraZeneca Plc rebuffed a similar overture from Pfizer Inc. Drugstore chain Walgreen Co. last week abandoned plans to change its address from Illinois to Switzerland when it completes a takeover of Alliance Boots GmbH.

Lew’s Warning

The Obama administration is trying to shut down such inversions after Treasury Secretary Jacob J. Lew warned of a hollowing out of the corporate tax base.

“We should prevent companies from effectively renouncing their citizenship to get out of paying taxes,” Lew wrote in a July 15 letter to lawmakers. “What we need as a nation is a new sense of economic patriotism.”

Because multinationals reap much of their earnings outside the U.S., where markets are less developed and business is growing faster, it makes sense to keep at least some of that money abroad.

One-percenters Intel Corp., General Electric Co. and Hewlett-Packard Co. keep cash abroad because that’s where business is growing.

“There’s a real need for us to maintain cash offshore,” Intel spokesman Chuck Mulloy said. “The cash is there because we need it there.”

Foreign Earnings

U.S. multinationals have accumulated $1.95 trillion in foreign earnings, up 11.8 percent from a year earlier, according to a Bloomberg study. In addition to prompting inversions, the money has sent companies on an overseas buying spree.

GE, which operates in more than 170 countries, is using $57 billion in un-repatriated profits to buy France’s Alstom SA. The deal will bring overseas acquisitions by U.S. companies to more than $75 billion in 2014, slightly ahead of last year’s pace, data compiled by Bloomberg show.

While the tax code gets blamed for dragging down the economy, freeing up foreign cash wouldn’t necessarily stimulate growth. When more than 843 companies including Pfizer, Oracle and Merck, repatriated $312 billion during a 2004 tax holiday, the hoped-for job creation never materialized. Instead, stock buybacks and executive pay rose, giving a lift to individual one-percenters.

Richest Americans

“If they ended up paying out this money to stockholders, the lion’s share is going to go to the top 1 percent of individuals,” said Thomas Hungerford, a senior economist at the Economic Policy Institute who wants to ban inversions. “But if you get the money back here and at least get it circulating, that will help the economy to some extent. It will certainly help our long-term federal budget problems.”

And the corporate 99 percent might reap the benefits.

“You could argue that companies that make a billion dollars and don’t pay taxes are freeloaders,” said Mitch Rofsky, president of the Better World Club, an insurer based in Portland, Oregon, and member of the American Sustainable Business Council, a group of small employers.

“It’s basically an issue of do our economic models work, is infrastructure supported, does government have the money it needs,” Rofsky said. “It’s unfair.”