What is the difference in future salary growth assumed under pension 2018 and 2019?
{"Actuarial benefit obligation -- Discount rate": {"Pension 2019": 3.2, "Other 2019": 2.95, "Pension 2018": 3.8, "Other 2018": 3.8}, "Benefit costs for the year ended -- Discount rate": {"Pension 2019": 3.9, "Other 2019": 3.9, "Pension 2018": 3.6, "Other 2018": 3.25}, "Benefit costs for the year ended -- Future salary growth": {"Pension 2019": 2.5, "Other 2019": "N/A", "Pension 2018": 2.5, "Other 2018": "N/A"}, "Benefit costs for the year ended -- Health care cost trend rate": {"Pension 2019": "N/A", "Other 2019": 3.49, "Pension 2018": "N/A", "Other 2018": 4.5}, "Benefit costs for the year ended -- Other medical trend rates": {"Pension 2019": "N/A", "Other 2019": 4.0, "Pension 2018": "N/A", "Other 2018": 4.5}}
future_salary_growth_2019 = df["Benefit costs for the year ended -- Future salary growth"]["Pension 2019"]
future_salary_growth_2018 = df["Benefit costs for the year ended -- Future salary growth"]["Pension 2018"]
answer = future_salary_growth_2019 - future_salary_growth_2018