What was the change in net pension asset from 2018 to 2019?
{"": {"2019": "\u00a3m", "2018": "\u00a3m"}, "Fair value of schemes assets": {"2019": 59.5, "2018": 56.4}, "Present value of funded schemes liabilities": {"2019": -53.9, "2018": -52.7}, "Retirement benefit asset recognised in the Statement of Financial Position": {"2019": 5.6, "2018": 3.7}, "Related deferred tax": {"2019": -0.9, "2018": -0.6}, "Net pension asset": {"2019": 4.7, "2018": 3.1}}
net_pension_asset_2019 = df["Net pension asset"]["2019"]
net_pension_asset_2018 = df["Net pension asset"]["2018"]
answer = net_pension_asset_2019 - net_pension_asset_2018