What was the percentage change in Basic weighted average number of common shares outstanding between 2018 and 2019?
{"Net income (loss)": {"2019": 18398.0, "2018": 16617.0, "2017": -7904.0}, "Basic weighted average number of common shares outstanding": {"2019": 34589.0, "2018": 35250.0, "2017": 35917.0}, "Effect of stock options and restricted stock units computed on -- treasury stock method": {"2019": 705.0, "2018": 889.0, "2017": "-"}, "Effect of stock options and restricted stock units computed on -- Diluted weighted average number of common shares outstanding": {"2019": 35294.0, "2018": 36139.0, "2017": 35917.0}, "Earnings (loss) per share: -- Basic": {"2019": 0.53, "2018": 0.47, "2017": -0.22}, "Earnings (loss) per share: -- Diluted": {"2019": 0.52, "2018": 0.46, "2017": -0.22}}
basic_weighted_average_number_of_common_shares_outstanding_2019 = df["Basic weighted average number of common shares outstanding"]["2019"]
basic_weighted_average_number_of_common_shares_outstanding_2018 = df["Basic weighted average number of common shares outstanding"]["2018"]
answer = ( basic_weighted_average_number_of_common_shares_outstanding_2019 - basic_weighted_average_number_of_common_shares_outstanding_2018 ) / basic_weighted_average_number_of_common_shares_outstanding_2018 * 100.0