What was the change in interest cost in 2019 from 2018?
{"Balance at the beginning of the period": {"2019": 3282, "2018": 3642}, "Service cost": {"2019": 405, "2018": 448}, "Interest cost": {"2019": 254, "2018": 196}, "Actuarial (gains) losses": {"2019": -108, "2018": -783}, "Benefits paid": {"2019": -22, "2018": -32}, "Effect of foreign currency translation": {"2019": 122, "2018": -189}, "Balance at the end of the period": {"2019": 3933, "2018": 3282}, "Unfunded status": {"2019": -3933, "2018": -3282}, "Net amount recognized": {"2019": -3933, "2018": -3282}}
interest_cost_2019 = df["Interest cost"]["2019"]
interest_cost_2018 = df["Interest cost"]["2018"]
answer = interest_cost_2019 - interest_cost_2018