What was the increase / (decrease) in the net revenue from 2018 to 2019?
{"Operating results -- Net revenue": {"2019": 140842.0, "2018": 127360.0, "2017": 127678.0, "2016": 120366.0, "2015": 103514.0}, "Operating results -- Gross profit": {"2019": 73880.0, "2018": 64417.0, "2017": 63785.0, "2016": 68106.0, "2015": 60081.0}, "Operating results -- Operating loss": {"2019": -13081.0, "2018": -12080.0, "2017": -11408.0, "2016": -4313.0, "2015": -12467.0}, "Operating results -- Operating loss, net of taxes": {"2019": -13164.0, "2018": -8350.0, "2017": -11721.0, "2016": -3765.0, "2015": -11497.0}, "Operating results -- Net loss": {"2019": -13164.0, "2018": -8350.0, "2017": -11721.0, "2016": -3765.0, "2015": -11497.0}, "Basic and diluted -- Net loss": {"2019": -0.57, "2018": -0.37, "2017": -0.52, "2016": -0.17, "2015": -0.51}, "Basic and diluted -- Weighted-average shares outstanding - basic and diluted": {"2019": 23037.0, "2018": 22801.0, "2017": 22615.0, "2016": 22483.0, "2015": 22338.0}, "Balance sheet data at year end -- Cash and cash equivalents": {"2019": 40771.0, "2018": 39943.0, "2017": 49255.0, "2016": 60608.0, "2015": 75067.0}, "Balance sheet data at year end -- Working capital": {"2019": 20707.0, "2018": 19343.0, "2017": 27183.0, "2016": 41401.0, "2015": 54407.0}, "Balance sheet data at year end -- Total assets": {"2019": 163591.0, "2018": 157207.0, "2017": 167305.0, "2016": 185157.0, "2015": 181525.0}, "Balance sheet data at year end -- Total debt": {"2019": 57.0, "2018": 177.0, "2017": 237.0, "2016": 333.0, "2015": 189.0}, "Balance sheet data at year end -- Total shareholders equity": {"2019": 100622.0, "2018": 108431.0, "2017": 113669.0, "2016": 123473.0, "2015": 124188.0}}
net_revenue_2019 = df["Operating results -- Net revenue"]["2019"]
net_revenue_2018 = df["Operating results -- Net revenue"]["2018"]
answer = net_revenue_2019 - net_revenue_2018