What is the percentage change in the charged to expense value of the company's liability insurance between 2018 and 2019?
{"Beginning balance": {"2019": 1.6, "2018": 1.5}, "Charged to expense": {"2019": 5.4, "2018": 5.8}, "Payments": {"2019": -5.5, "2018": -5.7}, "Ending balance": {"2019": 1.5, "2018": 1.6}}
charged_to_expense_2019 = df["Charged to expense"]["2019"]
charged_to_expense_2018 = df["Charged to expense"]["2018"]
answer = ( charged_to_expense_2019 - charged_to_expense_2018 ) / charged_to_expense_2018 * 100.0