What was the change in the Effect of other dilutive securities between 2018 and 2019?
{"Net income attributable to VMware, Inc.": {"January 31, 2020": 6412.0, "February 1, 2019": 1650.0, "February 2, 2018": 437.0}, "Weighted-average shares, basic for Classes A and B": {"January 31, 2020": 417058.0, "February 1, 2019": 413769.0, "February 2, 2018": 410315.0}, "Effect of other dilutive securities": {"January 31, 2020": 8177.0, "February 1, 2019": 7362.0, "February 2, 2018": 10572.0}, "Weighted-average shares, diluted for Classes A and B": {"January 31, 2020": 425235.0, "February 1, 2019": 421131.0, "February 2, 2018": 420887.0}, "Net income per weighted-average share attributable to VMware, Inc. common stockholders, basic for Classes A and B": {"January 31, 2020": 15.37, "February 1, 2019": 3.99, "February 2, 2018": 1.07}, "Net income per weighted-average share attributable to VMware, Inc. common stockholders, diluted for Classes A and B": {"January 31, 2020": 15.08, "February 1, 2019": 3.92, "February 2, 2018": 1.04}}
effect_2019 = df["Effect of other dilutive securities"]["February 1, 2019"]
effect_2018 = df["Effect of other dilutive securities"]["February 2, 2018"]
answer = effect_2019 - effect_2018