What is the percentage change in weighted average shares - basic in 2019 from 2018?
{"Weighted average shares - basic": {"2019": 30495, "2018": 27229, "2017": 27106}, "Effect of dilutive securities": {"2019": 111, "2018": 122, "2017": "\u2014"}, "Weighted average shares - diluted": {"2019": 30606, "2018": 27351, "2017": 27106}, "Number of anti-dilutive securities": {"2019": "\u2014", "2018": "\u2014", "2017": 967}}
weighted_average_shares_2019 = df["Weighted average shares - basic"]["2019"]
weighted_average_shares_2018 = df["Weighted average shares - basic"]["2018"]
answer = (weighted_average_shares_2019 - weighted_average_shares_2018) / weighted_average_shares_2018 * 100.0