What is the percentage change of Net debt from 2018 to 2019?
{"Short-term borrowings": {"2019": 98.9, "2018": 232.8}, "Current portion of long-term debt": {"2019": 16.7, "2018": 4.9}, "Total current debt": {"2019": 115.6, "2018": 237.7}, "Total long-term debt, less current portion(1)": {"2019": 3698.6, "2018": 3236.5}, "Total debt": {"2019": 3814.2, "2018": 3474.2}, "Less: Cash and cash equivalents": {"2019": -262.4, "2018": -271.7}, "Net debt": {"2019": 3551.8, "2018": 3202.5}}
net_debt_2019 = df["Net debt"]["2019"]
net_debt_2018 = df["Net debt"]["2018"]
answer = (net_debt_2019 - net_debt_2018) / net_debt_2018 * 100.0