A city's transportation department is interested in exploring the relationship between the outside temperature and the number of passengers that ride the bus line to better serve their customers. The manager recorded the temperature at the beginning of the hour and then had a bus driver record the number of passengers that boarded the bus throughout the hour. The correlation coefficient (r) was calculated to be -0.88. Use this value to determine the percentage of the variation in the number of passengers that cannot be explained by the outside temperature. Round your answer to the nearest whole number percentage.