What is the percentage change in goodwill at the end of the period at 2018 and 2019?
{"Year Ended December 31 -- ": {"2019": 2019, "2018": 2018}, "Year Ended December 31 -- Goodwill, beginning of period": {"2019": 3178, "2018": "$           -"}, "Year Ended December 31 -- Golden Ridge acquisition": {"2019": "-", "2018": 3178}, "Year Ended December 31 -- MGI acquistion": {"2019": 737, "2018": "-"}, "Year Ended December 31 -- Goodwill, end of period": {"2019": 3915, "2018": 3178}}
goodwill_end_2019 = df["Year Ended December 31 -- Goodwill, end of period"]["2019"]
goodwill_start_2019 = df["Year Ended December 31 -- Goodwill, beginning of period"]["2019"]
answer = ( goodwill_end_2019 - goodwill_start_2019 ) / goodwill_start_2019 * 100.0