What is the difference in revenue amount between 2019 and 2018?
{"Revenues": {"2019": 111412.0, "2018": 111322.0, "2017": 106524.0, "2016": 114263.0, "2015": 123961.0}, "Income from operations": {"2019": 9464.0, "2018": 8238.0, "2017": 4545.0, "2016": 10186.0, "2015": 3820.0}, "Income from continuing operations, net of taxes": {"2019": 4155.0, "2018": 4661.0, "2017": 1592.0, "2016": 6007.0, "2015": 8523.0}, "Income from discontinued operations, net of taxes": {"2019": "\u2014", "2018": "\u2014", "2017": 1938.0, "2016": 624.0, "2015": 2341.0}, "Net income": {"2019": 4155.0, "2018": 4661.0, "2017": 3530.0, "2016": 6631.0, "2015": 10864.0}, "Income per sharebasic: -- Continuing operations": {"2019": 0.35, "2018": 0.38, "2017": 0.12, "2016": 0.43, "2015": 0.58}, "Income per sharebasic: -- Discontinued operations": {"2019": "\u2014", "2018": "\u2014", "2017": 0.15, "2016": 0.04, "2015": 0.16}, "Income per sharebasic: -- Net income per share": {"2019": 0.35, "2018": 0.38, "2017": 0.27, "2016": 0.47, "2015": 0.74}, "Income per sharediluted: -- Continuing operations": {"2019": 0.35, "2018": 0.37, "2017": 0.12, "2016": 0.43, "2015": 0.58}, "Income per sharediluted: -- Discontinued operations": {"2019": "\u2014", "2018": "\u2014", "2017": 0.15, "2016": 0.04, "2015": 0.16}, "Income per sharediluted: -- Net income per share": {"2019": 0.35, "2018": 0.37, "2017": 0.27, "2016": 0.47, "2015": 0.74}, "Income per sharediluted: -- Shares used in per share calculation from continuing operations basic": {"2019": 11809.0, "2018": 12323.0, "2017": 12882.0, "2016": 13997.0, "2015": 14722.0}, "Income per sharediluted: -- Shares used in per share calculation from discontinued operations basic": {"2019": 11809.0, "2018": 12323.0, "2017": 12882.0, "2016": 13997.0, "2015": 14722.0}, "Income per sharediluted: -- Shares used in per share calculation from continuing operationsdiluted": {"2019": 12035.0, "2018": 12510.0, "2017": 12894.0, "2016": 13997.0, "2015": 14722.0}, "Income per sharediluted: -- Shares used in per share calculation from discontinuing operationsdiluted": {"2019": 12035.0, "2018": 12510.0, "2017": 12894.0, "2016": 13997.0, "2015": 14722.0}}
revenue_2019 = df["Revenues"]["2019"]
revenue_2018 = df["Revenues"]["2018"]
answer = revenue_2019 - revenue_2018