What was the change in total operating revenues?
{"Total operating revenues": {"2019": 218096, "2018": 127625, "Change": 90471, "% Change": 71}, "Vessel operating expenses": {"2019": -53689, "2018": -26317, "Change": -27372, "% Change": 104}, "Voyage expenses, charter-hire and commission expenses": {"2019": -460, "2018": -1363, "Change": 903, "% Change": -66}, "Administrative expenses": {"2019": -1371, "2018": 175, "Change": -1546, "% Change": -883}, "Project development expenses": {"2019": -2939, "2018": -16526, "Change": 13587, "% Change": -82}, "Depreciation and amortization": {"2019": -48088, "2018": -28193, "Change": -19895, "% Change": 71}, "Other operating (losses)/gains": {"2019": -28963, "2018": 2749, "Change": -31712, "% Change": -1154}, "Operating income": {"2019": 82586, "2018": 58150, "Change": 24436, "% Change": 42}, "Equity in net losses of affiliates": {"2019": "\u2014", "2018": -2047, "Change": 2047, "% Change": -100}}
total_revenue_2019 = df["Total operating revenues"]["2019"]
total_revenue_2018 = df["Total operating revenues"]["2018"]
answer = total_revenue_2019 - total_revenue_2018