pre_text: AMERICAN TOWER CORPORATION AND SUBSIDIARIES NOTES TO CONSOLIDATED FINANCIAL STATEMENTS (Tabular amounts in millions, unless otherwise disclosed) 18. EARNINGS PER COMMON SHARE The following table sets forth basic and diluted net income per common share computational data for the years ended December 31, (shares in thousands, except per share data):
table: 2019 2018 2017
table: Net income attributable to American Tower Corporation stockholders $1,887.8 $1,236.4 $1,238.9
table: Dividends on preferred stock — (9.4) (87.4)
table: Net income attributable to American Tower Corporation common stockholders $1,887.8 $1,227.0 $1,151.5
table: Basic weighted average common shares outstanding 442,319 439,606 428,181
table: Dilutive securities 3,201 3,354 3,507
table: Diluted weighted average common shares outstanding 445,520 442,960 431,688
table: Basic net income attributable to American Tower Corporation common stockholders per common share $4.27 $2.79 $2.69
table: Diluted net income attributable to American Tower Corporation common stockholders per common share $4.24 $2.77 $2.67
question: Analyse this data from a financial earnings document. What was the change in Dilutive securities between 2018 and 2019?