(Reuters) - BlackRock Inc will scrutinize how companies plan to use the cash they bring back to the United States as part of a tax holiday backed by U.S. President Donald Trump, CEO Larry Fink said in a letter distributed on Tuesday.

The BlackRock sign is pictured in the Manhattan borough of New York, in this October 11, 2015 file photo. REUTERS/Eduardo Munoz/Files

During his election campaign, Trump backed a policy of cutting taxes on cash that countries repatriate as a way to entice them to invest their overseas money in the United States.

Companies such as Apple Inc, Pfizer Inc, Microsoft Corp hold nearly $1.8 trillion overseas, Moody’s Investors Service Inc estimated last month. By doing so, they avoid a 35 percent U.S. corporate tax rate.

But Fink said the tax cuts may do little to boost economic growth as investors pile the cash into buying their shares back or paying a dividend, boosting their stock prices, but not hiring new employees or growing their businesses.

BlackRock oversees $5.1 trillion in assets, ranking as a top shareholder of many of the world’s largest companies. It votes on the composition of those companies’ boards as well as on governance proposals from management and shareholders.

“If tax reform also includes some form of reduced taxation for repatriation of cash trapped overseas, BlackRock will be looking to companies’ strategic frameworks for an explanation of whether they will bring cash back to the U.S. and if so, how they plan to use it,” Fink wrote in an annual letter to the CEOs of the S&P 500.

Fink also said U.S. lawmakers should raise the threshold at which capital gains on investments are taxed at a reduced rate, from one year to three years, to reward long-term investment.

Fink, who had donated to Democratic presidential candidate Hillary Clinton, recently joined an advisory council to Trump that includes several other CEOs.

In his letter Fink wrote how developments such as Brexit and new policies of U.S. President Donald Trump reflect “a growing backlash against the impact globalization and technological change are having on many workers and communities.” He also called on companies to do more to train employees.

Charles Elson, a University of Delaware finance professor who follows corporate governance issues, said the language shows how Trump’s rise has caused business leaders like Fink to pay attention to matters such as inequality.

“CEOs are responsive to the public,” Elson said. “His customers are the public and a healthy portion of the public has concerns about globalization.”