What was the average investment in cash and cash equivalents?
{"Cash and cash equivalents": {"2019": 1, "2018": 2}, "Equity securities": {"2019": 24, "2018": 27}, "Government debt securities": {"2019": 12, "2018": 3}, "Corporate debt securities": {"2019": 16, "2018": 26}, "Investments in funds(a)": {"2019": 21, "2018": 17}, "Real estate": {"2019": 2, "2018": 3}, "Other (mainly insurance assets  contracts and reserves)": {"2019": 24, "2018": 22}, "Total": {"2019": 100, "2018": 100}}
cash_2019 = df["Cash and cash equivalents"]["2019"]
cash_2018 = df["Cash and cash equivalents"]["2018"]
answer = (cash_2019 + cash_2018) / 2.0