What is the difference in equity instruments between 2018 and 2019?
{"": {"2019": "%", "2018": "%"}, "Equity instruments": {"2019": 53.9, "2018": 58.5}, "Debt instruments": {"2019": 18.6, "2018": 22.5}, "Real estate": {"2019": 10.8, "2018": 3.5}, "Cash and cash equivalents": {"2019": 3.7, "2018": 3.0}, "Other": {"2019": 13.0, "2018": 12.5}, "Total": {"2019": 100.0, "2018": 100.0}}
equity_instruments_2018 = df["Equity instruments"]["2018"]
equity_instruments_2019 = df["Equity instruments"]["2019"]
answer = equity_instruments_2018 - equity_instruments_2019