What is the percentage change of deferred sensor module revenues from 2018 to 2019?
{"Deferred license fees revenues": {"2019": 28, "2018": "$-"}, "Deferred NRE revenues": {"2019": 20, "2018": "-"}, "Deferred AirBar revenues": {"2019": 6, "2018": 59}, "Deferred sensor modules revenues": {"2019": 13, "2018": 16}, "": {"2019": 67, "2018": 75}}
deferred_sensor_modules_revenues_2019 = df["Deferred sensor modules revenues"]["2019"]
deferred_sensor_modules_revenues_2018 = df["Deferred sensor modules revenues"]["2018"]
answer = ( deferred_sensor_modules_revenues_2019 - deferred_sensor_modules_revenues_2018 ) / deferred_sensor_modules_revenues_2018 * 100.0