The legendary investor also devoted a portion of his annual shareholder letter to pointing out some of his biggest mistakes Billionaire investor Warren Buffett used his annual letter to laud immigrants and their contribution to the growth of the US economy amid President Donald Trump’s anti-immigrant stance. “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,” he wrote in the letter to shareholders of his massive Berkshire Hathaway conglomerate.