What was the change in Corporate in 2019 from 2018?
{"": {"2019": "Number", "2018": "Number"}, "Customer operations": {"2019": 370, "2018": 380}, "Product and technology": {"2019": 317, "2018": 312}, "Corporate": {"2019": 115, "2018": 130}, "Total": {"2019": 802, "2018": 822}}
corporate_2019 = df["Corporate"]["2019"]
corporate_2018 = df["Corporate"]["2018"]
answer = corporate_2019 - corporate_2018