What was the change in Other non-current liabilities between 2018 and 2019?
{"Accounts receivable": {"December 31, 2019": 80.5, "December 31, 2018 (1)": 92.6}, "Prepaids and other current assets": {"December 31, 2019": 8.3, "December 31, 2018 (1)": 7.7}, "Notes receivable and other non-current assets": {"December 31, 2019": 21.3, "December 31, 2018 (1)": 22.2}, "Unearned revenue (2)": {"December 31, 2019": 35.0, "December 31, 2018 (1)": 35.0}, "Other non-current liabilities (3)": {"December 31, 2019": 79.0, "December 31, 2018 (1)": 54.1}}
other_noncurrent_liabilities_2019 = df["Other non-current liabilities (3)"]["December 31, 2019"]
other_noncurrent_liabilities_2018 = df["Other non-current liabilities (3)"]["December 31, 2018 (1)"]
answer = other_noncurrent_liabilities_2019 - other_noncurrent_liabilities_2018