What was the change in Short-term investments in 2019 from 2018?
{"Cash and cash equivalents": {"2019": 305833, "2018": 310495}, "Short-term investments": {"2019": 120, "2018": 120}, "Working capital": {"2019": 854507, "2018": 865664}}
shortterm_investments_2019 = df["Short-term investments"]["2019"]
shortterm_investments_2018 = df["Short-term investments"]["2018"]
answer = shortterm_investments_2019 - shortterm_investments_2018