Of all the cities in the US with a population of at least 250,000, the most 'central' in some ways is Cincinnati, as it has the highest share of the country's population that can drive there within a one-day drive (using the trucker's 11 hour work day as the measure). What % of the country's population could drive to Cincinnati in one day as of 2014 when the analysis was performed? We'll accept responses within 5% of the correct answer.

Fact: Ninety percent of Earth's population lives in the Northern Hemisphere.