What is the percentage change of the effective tax rate from 2018 to 2019?
{"Statutory federal income tax rate": {"Dec 28, 2019": 21.0, "Dec 29, 2018": 21.0, "Dec 30, 2017": 35.0}, "Increase (reduction) in rate resulting from: -- Non-U.S. income taxed at different rates": {"Dec 28, 2019": -3.7, "Dec 29, 2018": -3.6, "Dec 30, 2017": -7.6}, "Increase (reduction) in rate resulting from: -- Research and development tax credits": {"Dec 28, 2019": -2.3, "Dec 29, 2018": -2.7, "Dec 30, 2017": -2.3}, "Increase (reduction) in rate resulting from: -- Domestic manufacturing deduction benefit": {"Dec 28, 2019": "\u2014", "Dec 29, 2018": "\u2014", "Dec 30, 2017": -1.3}, "Increase (reduction) in rate resulting from: -- Foreign derived intangible income benefit": {"Dec 28, 2019": -3.2, "Dec 29, 2018": -3.7, "Dec 30, 2017": "\u2014"}, "Increase (reduction) in rate resulting from: -- Tax Reform": {"Dec 28, 2019": "\u2014", "Dec 29, 2018": -1.3, "Dec 30, 2017": 26.8}, "Increase (reduction) in rate resulting from: -- ISecG divestiture": {"Dec 28, 2019": "\u2014", "Dec 29, 2018": "\u2014", "Dec 30, 2017": 3.3}, "Increase (reduction) in rate resulting from: -- Other": {"Dec 28, 2019": 0.7, "Dec 29, 2018": -0.1, "Dec 30, 2017": -1.1}, "Increase (reduction) in rate resulting from: -- Effective tax rate": {"Dec 28, 2019": 12.5, "Dec 29, 2018": 9.7, "Dec 30, 2017": 52.8}}
effective_tax_rate_2019 = df["Increase (reduction) in rate resulting from: -- Effective tax rate"]["Dec 28, 2019"]
effective_tax_rate_2018 = df["Increase (reduction) in rate resulting from: -- Effective tax rate"]["Dec 29, 2018"]
answer = ( effective_tax_rate_2019 - effective_tax_rate_2018 ) / effective_tax_rate_2018 * 100.0