What is the increase / (decrease) in the orders for Asia and Australia from 2018 to 2019?
{"Europe, C. I. S., Africa, Middle East": {"2019": 44360, "2018": 42782, "Actual": 4, "Comp.": 4}, "therein: Germany": {"2019": 12282, "2018": 11729, "Actual": 5, "Comp.": 4}, "Americas": {"2019": 23796, "2018": 22115, "Actual": 8, "Comp.": 3}, "therein: U. S.": {"2019": 17993, "2018": 16012, "Actual": 12, "Comp.": 6}, "Asia, Australia": {"2019": 18693, "2018": 18147, "Actual": 3, "Comp.": 2}, "therein: China": {"2019": 8405, "2018": 8102, "Actual": 4, "Comp.": 3}, "Siemens": {"2019": 86849, "2018": 83044, "Actual": 5, "Comp.": 3}, "therein: emerging markets1": {"2019": 27607, "2018": 28272, "Actual": -2, "Comp.": -2}}
asia_australia_2019 = df["Asia, Australia"]["2019"]
asia_australia_2018 = df["Asia, Australia"]["2018"]
answer = asia_australia_2019 - asia_australia_2018