What was the change in effect of surplus cap in 2019 from 2018?
{"": {"2019": "\u00a3m", "2018": "\u00a3m"}, "Present value of funded obligations": {"2019": 20.0, "2018": 19.7}, "Fair value of plan assets": {"2019": -22.2, "2018": -21.0}, "Effect of surplus cap": {"2019": 2.2, "2018": 1.3}, "Net asset recognised in the Consolidated balance sheet": {"2019": "\u2013", "2018": "\u2013"}}
effect_of_surplus_cap_2019 = df["Effect of surplus cap"]["2019"]
effect_of_surplus_cap_2018 = df["Effect of surplus cap"]["2018"]
answer = effect_of_surplus_cap_2019 - effect_of_surplus_cap_2018