Billionaire investor Warren Buffett, wading into the national debate over immigration, said the “miraculous” achievements of the U.S. economy since its founding can be attributed in part to people who had the courage to leave their home countries for America.

“From a standing start 240 years ago -- a span of time less than triple my days on earth -- Americans have combined human ingenuity, a market system, a tide of talented and ambitious immigrants, and the rule of law to deliver abundance beyond any dreams of our forefathers,” Buffett, chairman and chief executive officer of Berkshire Hathaway Inc., wrote in his annual letter to shareholders posted online on Saturday.

Buffett didn’t mention President Donald Trump in the letter, which offered a full-throated defense of the American market system, describing it as an “economic traffic cop ably directing capital, brains and labor” to create the nation’s wealth.

“Governmental redirection, through federal, state and local taxation, has in addition determined the distribution of a significant portion of the bounty,” he wrote, citing programs that support seniors and public education for children.

Sprawling Conglomerate

Buffett has long been bullish on the prospects for businesses in the U.S. and few have benefited more than he has from the nation’s economic prosperity. Over the past five decades, he amassed a $76 billion fortune building Berkshire into a sprawling conglomerate with interests in insurance, energy, manufacturing, media, retail and transportation.

Berkshire’s Class A shares have climbed 15 percent since Election Day, bringing the company’s market capitalization above $400 billion for the first time.

Read Warren Buffett’s annual letter here.

In last year’s letter, Buffett wrote sweepingly about why the country had a bright future, rebutting much of the economic pessimism that dominated Trump’s successful campaign for the presidency.

Since taking office last month, Trump has continued to paint a bleak picture. His inaugural speech painted an ominous portrait of the nation as a place of violent “American carnage” where “rusted-out factories” are “scattered like tombstones” and the middle class’s wealth is “ripped from their homes.”

While Buffett, 86, supported Democrat Hillary Clinton in the presidential election, he’s a widely respected business leader who has relationships with elected officials on both sides of the political aisle. The billionaire frequently clashed with Trump during the campaign and scolded him for not releasing income-tax returns, as major party presidential candidates have done for roughly four decades.

Since the election, Buffett has struck a more conciliatory tone and called for unity. In an interview with CNN in November, he said that people could disagree with Trump, but ultimately the president “deserves everybody’s respect.”

Trump entered office last month with the lowest approval ratings for an incoming president in at least four decades. His weeks-old administration has been met with mass protests, contentious confirmation hearings for his cabinet picks and a legal showdown over a controversial immigration order.