Paul Joubert retired from his firm. He has continued to hold his private retirement investments in a portfolio of common stocks and bonds. At the beginning of 2015, when he retired, his account was valued at 453,000. By the end of 2015, the value of his account was 523,500. Joubert made no contributions to or withdrawals from the portfolio during 2015. What rate of return did Joubert earn on his portfolio during 2015?