No serious attempt has been made to estimate the total cost of free roads (nor will one be made here) but it likely runs into the trillions. For example, consider the sums likely spent by the federal government on building the interstate highway system. One partial estimate of this expense—which excludes many important federal highways and does not include maintenance or expansions, or, of course, state, county, and local roads—exceeds half a trillion dollars in 2019 dollars, calculated from 2006 dollars using the Consumer Price Index (“CPI”) Inflation Calculator published by the U.S. Bureau of Labor Statistics.220 Meanwhile, of the amount spent on local (noninterstate) roads in one recent year ($39.65 billion in 2019 dollars, calculated from 2002 dollars using the CPI Inflation Calculator), 89% was paid by the general taxpayer and only 11% by motorists themselves. At this rate, state and local governments would spend half a trillion dollars on roads every thirteen years.