What is the change between 2018 and 2019 average actuarial losses recognised in the SOCI?
{"Current service cost": {"2019 m": 31, "2018 m": 34, "2017 m": 43}, "Past service costs1": {"2019 m": 16, "2018 m": 2, "2017 m": -27}, "Net interest charge": {"2019 m": 10, "2018 m": 8, "2017 m": 4}, "Total included within staff costs": {"2019 m": 57, "2018 m": 44, "2017 m": 20}, "Actuarial losses recognised in the SOCI": {"2019 m": 33, "2018 m": 94, "2017 m": 274}}
actuarial_losses_recognised_2019 = df["Actuarial losses recognised in the SOCI"]["2019 m"]
actuarial_losses_recognised_2018 = df["Actuarial losses recognised in the SOCI"]["2018 m"]
past_service_costs_2018 = df["Past service costs1"]["2018 m"]
answer = ( ( actuarial_losses_recognised_2019 + actuarial_losses_recognised_2018 ) / past_service_costs_2018 ) - ( ( actuarial_losses_recognised_2018 + df["Actuarial losses recognised in the SOCI"]["2017 m"] ) / past_service_costs_2018 )