What was the change in Basic weighted average shares outstanding between 2018 and 2019?
{"Weighted average shares outstanding: -- Basic weighted average shares outstanding": {"2019": 116175, "2018": 116057, "2017": 118059}, "Add: Dilutive effect of stock options, RSUs, and contingently issuable -- shares": {"2019": 2396, "2018": 1575, "2017": 1385}, "Add: Dilutive effect of stock options, RSUs, and contingently issuable -- Diluted weighted average shares outstanding": {"2019": 118571, "2018": 117632, "2017": 119444}}
basic_weighted_average_shares_outstanding_2019 = df["Weighted average shares outstanding: -- Basic weighted average shares outstanding"]["2019"]
basic_weighted_average_shares_outstanding_2018 = df["Weighted average shares outstanding: -- Basic weighted average shares outstanding"]["2018"]
answer = basic_weighted_average_shares_outstanding_2019 - basic_weighted_average_shares_outstanding_2018