What is the change in Weighted-average shares used to compute basic EPS from 2018 and 2019?
{"Numerator: -- Netearnings": {"2019": 159407.0, "2018": 163677.0, "2017": 90683.0}, "Denominator: -- Weighted-average shares used to compute basic EPS": {"2019": 35538.0, "2018": 35586.0, "2017": 35741.0}, "Dilutive potential common shares due to dilutive: -- RSUs, net of tax effect": {"2019": 421.0, "2018": 423.0, "2017": 466.0}, "Dilutive potential common shares due to dilutive: -- Weighted-average shares used to compute diluted EPS": {"2019": 35959.0, "2018": 36009.0, "2017": 36207.0}, "Net earnings per share: -- Basic": {"2019": 4.49, "2018": 4.6, "2017": 2.54}, "Net earnings per share: -- Diluted": {"2019": 4.43, "2018": 4.55, "2017": 2.5}}
denominator_weighted_average_shares_used_to_compute_basic_eps_2019 = df["Denominator: -- Weighted-average shares used to compute basic EPS"]["2019"]
denominator_weighted_average_shares_used_to_compute_basic_eps_2018 = df["Denominator: -- Weighted-average shares used to compute basic EPS"]["2018"]
answer = denominator_weighted_average_shares_used_to_compute_basic_eps_2019 - denominator_weighted_average_shares_used_to_compute_basic_eps_2018