What was the change in current portion of debt between 2016 and 2017?
{"Balance Sheet Data: -- Working capital": {"2019 (1)(2)": 308426, "2018 (3)": 269857, "2017": 100039, "2016 (5)": 31625, "2015": -2360}, "Balance Sheet Data: -- Total assets": {"2019 (1)(2)": 3257534, "2018 (3)": 2122455, "2017": 1861639, "2016 (5)": 1902295, "2015": 1975788}, "Balance Sheet Data: -- Current portion of debt (6)": {"2019 (1)(2)": 34148, "2018 (3)": 20767, "2017": 17786, "2016 (5)": 90323, "2015": 89710}, "Balance Sheet Data: -- Debt (long-term portion) (6)": {"2019 (1)(2)": 1350592, "2018 (3)": 658602, "2017": 668356, "2016 (5)": 656063, "2015": 845639}, "Balance Sheet Data: -- Stockholders equity": {"2019 (1)(2)": 1129968, "2018 (3)": 1048231, "2017": 764597, "2016 (5)": 754917, "2015": 654400}}
current_portion_of_debt_2016 = df["Balance Sheet Data: -- Current portion of debt (6)"]["2016 (5)"]
current_portion_of_debt_2017 = df["Balance Sheet Data: -- Current portion of debt (6)"]["2017"]
answer = current_portion_of_debt_2016 - current_portion_of_debt_2017