"When U.S. companies say, 'U.S. companies will win,' you have to ask, 'Who will win?,' " Sanchirico said.
The issue is anything but academic.
Multinationals are U.S. corporations with significant operations in other nations. The problem centers on the longtime practice of such U.S multinationals as Google, Apple, and others of sheltering a share of their profit in overseas tax havens such as Bermuda, the Cayman Islands, and the British Virgin Islands. Those companies and others have an estimated $1.9 trillion parked in foreign tax havens, Sanchirico says.
As a consequence, the money is beyond the reach of U.S. tax officials. Sanchirico says that, while business advocates often propose cutting corporate taxes as a way of inducing companies to abandon tax havens, it is not at all clear how much of the money would end up in the United States if taxes were cut.
The issue, though abstruse, has generated interest from President Obama, Capitol Hill, and foreign governments - if only because so much money is at stake.
Rep. Dave Camp (R., Mich.), the chairman of the House Ways and Means Committee, has proposed a package of tax overhauls seeking to address the tax-sheltered earnings of American corporations overseas. He would do this, in part, by lowering the U.S. corporate tax rate from 35 percent to 25 percent as a way to induce companies to keep their earnings in the U.S.
The Senate held a hearing in 2013 in which Apple's practice of parking profit overseas was closely scrutinized.
But, Sanchirico points out, it's hard to know who would benefit.
"The existing constellation of disclosures and reports about the ownership of U.S. equity, though in some respects surprisingly detailed, reveals almost nothing about the foreign ownership share of large U.S multinationals," Sanchirico says in the study.
He offers no opinion on the advisability of tax cuts for multinationals, offered as a way to induce them to bring their earnings home. But he says lawmakers should at least know where the benefits of lower taxes on companies' overseas profit might flow before enacting them.
Sanchirico's analysis encompassed a broad range of databases, academic studies, and surveys by the U.S. Treasury Department. Some foreign investors, notably Norway, whose $818 billion sovereign wealth fund is the world's largest, are relatively transparent. Norway has holdings of about $149 billion in U.S.-based companies.
But other sovereign funds, such as those based in the Middle East and China, tell very little. Sanchirico says those who manage these sovereign funds may believe they run a political risk in other nations if the source of the investment became known.
It is likely the case that the multinational corporations themselves don't even know to what degree they are owned by foreign shareholders. That is because companies usually do not know the identities of shareholders who purchase shares through a brokerage, Sanchirico says.
Tax lawyers in the U.S. and abroad employ exotic avoidance strategies with names such as the "double Irish, Dutch sandwich," Sanchirico's study points out. The tactic is available only to multinational companies, since, to make the strategy work, American companies not designated as multinationals must show to U.S. officials that they have overseas operations, Sanchirico says.
The first stop typically is Ireland, whose pliable tax statutes permit American companies to establish subsidiaries that then are positioned to take advantage of favorable tax regimes in what Sanchirico calls "low- or no-tax islands," such as the Caymans or Bermuda.
"There are things that a multinational corporation can do to shift profitable aspects of their business to international jurisdictions," Sanchirico said. "It is a complicated constellation of treaties that allows this. It is no one thing."