What was the change in retained earnings in 2019 from 2018?
{"RELATIVE IMPORTANCE OF SPEND ON PAY -- Expenditure USDm": {"2019": 2019, "2018": 2018, "2017": 2017}, "RELATIVE IMPORTANCE OF SPEND ON PAY -- Dividends paid": {"2019": "-", "2018": "-", "2017": 1.2}, "RELATIVE IMPORTANCE OF SPEND ON PAY -- Purchase of outstanding treasury shares in TORM A/S": {"2019": "-", "2018": "-", "2017": "-"}, "RELATIVE IMPORTANCE OF SPEND ON PAY -- Purchase/disposals of treasury shares": {"2019": "-", "2018": "-", "2017": "-"}, "RELATIVE IMPORTANCE OF SPEND ON PAY -- Total": {"2019": "-", "2018": "-", "2017": 1.2}, "RELATIVE IMPORTANCE OF SPEND ON PAY -- Staff costs": {"2019": 45.8, "2018": 46.2, "2017": 43.8}, "RELATIVE IMPORTANCE OF SPEND ON PAY -- Retained earnings": {"2019": 920.0, "2018": 752.0, "2017": 786.0}}
retained_earnings_2019 = df["RELATIVE IMPORTANCE OF SPEND ON PAY -- Retained earnings"]["2019"]
retained_earnings_2018 = df["RELATIVE IMPORTANCE OF SPEND ON PAY -- Retained earnings"]["2018"]
answer = retained_earnings_2019 - retained_earnings_2018