What was the change in Beginning balance, as of January 1 in 2019 from 2018?
{"Beginning balance, as of January 1": {"2019": 43395, "2018": 36263, "2017": 38958}, "Additions: -- Tax positions for current year": {"2019": 1322, "2018": 4716, "2017": 8208}, "Additions: -- Tax positions for prior years": {"2019": 8043, "2018": 2626, "2017": 199}, "Reductions: -- Tax positions for prior years": {"2019": -31397, "2018": -153, "2017": -10573}, "Reductions: -- Expiration of statutes": {"2019": -183, "2018": -57, "2017": -325}, "Reductions: -- Settlements with tax authorities": {"2019": "\u2014", "2018": "\u2014", "2017": -204}, "Reductions: -- Ending balance, as of December 31": {"2019": 21180, "2018": 43395, "2017": 36263}}
beginning_balance_2019 = df["Beginning balance, as of January 1"]["2019"]
beginning_balance_2018 = df["Beginning balance, as of January 1"]["2018"]
answer = beginning_balance_2019 - beginning_balance_2018