What is the change in the Weighted average common shares outstanding-basic from 2018 to 2019?
{"Numerator:      -- Loss from continuing operations": {"2019": -383798.0, "2018": -133762.0, "2017": -150416.0}, "Numerator:      -- Loss from discontinued operations": {"2019": "\u2014", "2018": -6215.0, "2017": -19077}, "Numerator:      -- Net loss": {"2019": -383798.0, "2018": -139977.0, "2017": -169493.0}, "Numerator:      -- Warrant liability gain": {"2019": "\u2014", "2018": -27646.0, "2017": "\u2014"}, "Numerator:      -- Net loss attributable to common stockholders": {"2019": -383798.0, "2018": -167623.0, "2017": -169493.0}, "Denominator:      -- Weighted average common shares outstanding-basic": {"2019": 65686.0, "2018": 64741.0, "2017": 60704.0}, "Denominator:      -- Dilutive effect of warrants": {"2019": "\u2014", "2018": 570.0, "2017": "\u2014"}, "Denominator:      -- Weighted average common shares outstanding-diluted": {"2019": 65686.0, "2018": 65311.0, "2017": 60704.0}, "Common stock earnings per share-basic:      -- Continuing operations": {"2019": -5.84, "2018": -2.07, "2017": -2.48}, "Common stock earnings per share-basic:      -- Discontinued operations": {"2019": "\u2014", "2018": -0.1, "2017": -0.31}, "Common stock earnings per share-basic:      -- Net common stock earnings per share-basic": {"2019": -5.84, "2018": -2.16, "2017": -2.79}, "Common stock earnings per share-diluted: -- Continuing operations": {"2019": -5.84, "2018": -2.47, "2017": -2.48}, "Common stock earnings per share-diluted: -- Discontinued operations": {"2019": "\u2014", "2018": -0.1, "2017": -0.31}, "Common stock earnings per share-diluted: -- Net common stock earnings per share-diluted": {"2019": -5.84, "2018": -2.57, "2017": -2.79}}
denominator_2019 = df["Denominator:      -- Weighted average common shares outstanding-basic"]["2019"]
denominator_2018 = df["Denominator:      -- Weighted average common shares outstanding-basic"]["2018"]
answer = denominator_2019 - denominator_2018