What is the percentage change in net operating loss carryforward in 2018 and 2019?
{"December 31 -- ": {"2019": 2019, "2018": 2018}, "December 31 -- Net operating loss carryforwards": {"2019": 7672, "2018": 4541}, "December 31 -- Stock options and warrants": {"2019": 420, "2018": 214}, "December 31 -- Property": {"2019": 138, "2018": 299}, "December 31 -- Intangible assets": {"2019": 66, "2018": 94}, "December 31 -- Capitalized expenses": {"2019": 54, "2018": 86}, "December 31 -- Other": {"2019": 210, "2018": 164}, "December 31 -- Operating right-of-use lease assets": {"2019": -667, "2018": ""}, "December 31 -- Operating right-of-use lease liabilities": {"2019": 794, "2018": ""}, "December 31 -- Net deferred tax assets": {"2019": 8687, "2018": 5398}, "December 31 -- Less: Valuation allowance": {"2019": -8687, "2018": -5398}, "December 31 -- Deferred tax asset (liability)": {"2019": "$             -", "2018": "$             -"}}
net_operating_loss_carryforward_2019 = df["December 31 -- Net operating loss carryforwards"]["2019"]
net_operating_loss_carryforward_2018 = df["December 31 -- Net operating loss carryforwards"]["2018"]
answer = ( net_operating_loss_carryforward_2019 - net_operating_loss_carryforward_2018 ) / net_operating_loss_carryforward_2018 * 100.0