What is the value of the voyage revenue in 2017 as a percentage of the revenue in 2018?
{"Voyage Revenue  ": {"2018": 289016.0, "2017": 297141.0, "Variance ": -2.7}, "Less Voyage expenses  ": {"2018": -165012.0, "2017": -142465.0, "Variance ": 15.8}, "Net Voyage Revenue  ": {"2018": 124004.0, "2017": 154676.0, "Variance ": -19.8}, "Vessel Calendar Days (1)  ": {"2018": 9747.0, "2017": 10892.0, "Variance ": -10.5}, "Less off-hire days  ": {"2018": 277.0, "2017": 867.0, "Variance ": -68.1}, "Total TCE days  ": {"2018": 9470.0, "2017": 10025.0, "Variance ": -5.5}, "TCE Rate per day (2) ": {"2018": 13095.0, "2017": 15428.0, "Variance ": -15.1}, "Total Days for vessel operating expenses  ": {"2018": 9747.0, "2017": 10892.0, "Variance ": -10.5}}
voyage_revenue_2017 = df["Voyage Revenue  "]["2017"]
voyage_revenue_2018 = df["Voyage Revenue  "]["2018"]
answer = voyage_revenue_2017 / voyage_revenue_2018 * 100.0