What is the increase in the fair value of plan assets from 2018 to 2019?
{"Fair value of plan assets": {"2019": 90365, "2018": 84718}, "Less: projected benefit obligations": {"2019": 143662, "2018": 128915}, "Underfunded status": {"2019": -53297, "2018": -44197}}
fair_value_2019 = df["Fair value of plan assets"]["2019"]
fair_value_2018 = df["Fair value of plan assets"]["2018"]
answer = fair_value_2019 - fair_value_2018