What was the change in Short-term deposits and highly liquid funds between 2018 and 2019?
{"Cash on hand and at banks": {"December 31, 2019": 77041, "December 31,2018": 131432}, "Short-term deposits and highly liquid funds": {"December 31, 2019": 950, "December 31,2018": 6450}, "Restricted cash": {"December 31, 2019": 736, "December 31,2018": 12892}, "Cash and cash equivalents and restricted cash": {"December 31, 2019": 78727, "December 31,2018": 150774}}
short_term_deposits_2019 = df["Short-term deposits and highly liquid funds"]["December 31, 2019"]
short_term_deposits_2018 = df["Short-term deposits and highly liquid funds"]["December 31,2018"]
answer = short_term_deposits_2019 - short_term_deposits_2018