Traders work on the floor at the New York Stock Exchange (NYSE) in New York, U.S., March 2, 2020.Brendan McDermid/Reuters The S&P 500 ended at a record high Thursday to cap off its strongest first quarter in five years on Thursday. Initial filings for unemployment came in lower than expected for the week up to March 16. The latest GDP estimate for the fourth quarter came in at 3.4% year-over-year. US stocks were little changed on Thursday, closing mixed to end a short week, though each of the three benchmark indexes capped off winning months and quarters.The benchmark S&P 500 closed at a record high, cementing its best first quarter since 2019 after climbing more than 10.7% in the three-month stretch.Initial unemployment filings for the week ending March 16 came in lower than expected at 210,000 versus the 211,000 expected by Dow Jones estimates.