What was the increase / (decrease) in the short term loan from 2018 to 2019?
{"($ in millions) -- At December 31:": {"2019": 2019, "2018": 2018}, "($ in millions) -- Commercial paper": {"2019": 304, "2018": 2995}, "($ in millions) -- Short-term loans": {"2019": 971, "2018": 161}, "($ in millions) -- Long-term debtcurrent maturities": {"2019": 7522, "2018": 7051}, "($ in millions) -- Total": {"2019": 8797, "2018": 10207}}
short_term_loan_2019 = df["($ in millions) -- Short-term loans"]["2019"]
short_term_loan_2018 = df["($ in millions) -- Short-term loans"]["2018"]
answer = short_term_loan_2019 - short_term_loan_2018