What was the increase / (decrease) in the Other costs from 2018 to 2019?
{"($ in millions) -- For the year ended December 31:": {"2019": 2019, "2018": 2018, "Yr.-to-Yr. Percent Change": "Yr.-to-Yr. Percent Change"}, "Retirement-related planscost -- Service cost": {"2019": 385.0, "2018": 431.0, "Yr.-to-Yr. Percent Change": -10.7}, "Retirement-related planscost -- Multi-employer plans": {"2019": 32.0, "2018": 38.0, "Yr.-to-Yr. Percent Change": -16.9}, "Retirement-related planscost -- Cost of defined contribution plans": {"2019": 1040.0, "2018": 1024.0, "Yr.-to-Yr. Percent Change": 1.5}, "Retirement-related planscost -- Total operating costs/ (income)": {"2019": 1457.0, "2018": 1494.0, "Yr.-to-Yr. Percent Change": -2.5}, "Retirement-related planscost -- Interest cost": {"2019": 2929.0, "2018": 2726.0, "Yr.-to-Yr. Percent Change": 7.4}, "Retirement-related planscost -- Expected return on plan assets": {"2019": -4192.0, "2018": -4049.0, "Yr.-to-Yr. Percent Change": 3.5}, "Retirement-related planscost -- Recognized actuarial losses": {"2019": 1819.0, "2018": 2941.0, "Yr.-to-Yr. Percent Change": -38.2}, "Retirement-related planscost -- Amortization of prior service costs/(credits)": {"2019": -9.0, "2018": -73.0, "Yr.-to-Yr. Percent Change": -87.6}, "Retirement-related planscost -- Curtailments/settlements": {"2019": 41.0, "2018": 11.0, "Yr.-to-Yr. Percent Change": 262.2}, "Retirement-related planscost -- Other costs": {"2019": 28.0, "2018": 16.0, "Yr.-to-Yr. Percent Change": 76.2}, "Retirement-related planscost -- Total non-operating costs/(income)": {"2019": 615.0, "2018": 1572.0, "Yr.-to-Yr. Percent Change": -60.9}, "Retirement-related planscost -- Total retirement-related planscost": {"2019": 2072.0, "2018": 3066.0, "Yr.-to-Yr. Percent Change": -32.4}}
retirement_related_plans_cost_2019 = df["Retirement-related planscost -- Other costs"]["2019"]
retirement_related_plans_cost_2018 = df["Retirement-related planscost -- Other costs"]["2018"]
answer = retirement_related_plans_cost_2019 - retirement_related_plans_cost_2018