Goldman says boost from tax cut 'behind us' so buy these companies that can grow on their own

"The boost from lower tax rates is likely behind us," Goldman's chief U.S. equity strategist wrote. Stock profits will be harder to come by in 2019 as corporations will no longer get a boost from lower corporate tax rates, according to Goldman Sachs. David Kostin, the bank's chief U.S. equity strategist, said in a note Friday that an increase in the S&P 500's return on equity "appears unlikely" this year.