What was the change in contract liabilities between 2018 and 2019?
{"Accrued product-related costs": {"2019": 4464, "2018": 4377}, "Accrued income taxes": {"2019": 7903, "2018": 6914}, "Accrued property and other taxes": {"2019": 1574, "2018": 1976}, "Accrued professional fees": {"2019": 1599, "2018": 3350}, "Contract liabilities": {"2019": 2877, "2018": 1981}, "Dividends payable": {"2019": 1299, "2018": 1310}, "Remediation reserves": {"2019": 11444, "2018": 11274}, "Other accrued liabilities": {"2019": 5218, "2018": 6165}, "Total accrued expenses and other liabilities": {"2019": 36378, "2018": 37347}}
contract_liabilities_2019 = df["Contract liabilities"]["2019"]
contract_liabilities_2018 = df["Contract liabilities"]["2018"]
answer = contract_liabilities_2019 - contract_liabilities_2018