Much has been made over the attendance at the march and rally in Washington, D.C., on September 12. Reports varied, with many on the Left clinging to an unofficial D.C. Fire Department estimate of 60,000 to 70,000. Some reports from overseas went as far as to say 2 million. However, one completely objective source of information is the number of people who rode Metro, D.C.’s subway system. Washington Metro measures and releases its ridership numbers and these numbers have been used in the past to judge the size of major events in Washington, D.C.

For a fair comparison, we looked at the Saturday after Labor Day in 2008, which is when September 12 fell in 2009. On September 12, 2009, 437,624 rode metro rail. By comparison, on the Saturday after Labor Day in 2008, 202,528 rode. The difference is 235,096.  Even if nobody else came to the march—and we know they did by chartered bus and by carpool—the theory that only 70,000 people were there is off by roughly 335 percent. To take the comparison a step further, we also looked at the attendance for President Obama’s inauguration in January 2009. Conventional wisdom estimates that attendance for the inaugural was between 800,000 and 1.8 million, or an average of 1.3 million.

If you compare Metro riders on Inauguration Day 2009 to Martin Luther King Day 2008, the similarly situated federal holiday in January, then you find that approximately 975,000 additional people rode metro for the inauguration. So, if you compare 975,000 additional metro riders as a percentage of the 1.3 million who attended the inauguration and you do the same math for 235,000 additional metro riders for the 9/12 March, than at least 313,000 went downtown for the explicit purpose of marching against out-of-control government spending on September 12. This assumes a similar percentage of attendees took buses, cabs, drove in, walked, etc.

If you believe the number was 1.8 million at the Inauguration and you do the same math for 9/12, then the number is 433,000. So is an estimate of 313,000 to 433,000 attendees accurate? Well, it is certainly an unbiased and impartial start to understanding the debate over crowd size. The bottom line is that hundreds of thousands of Americans who were upset with government spending, a failed stimulus, a government takeover of health care, and a massive energy tax came with their parents, children, grandparents, cousins, college roommates, etc. to a multi-generational and peaceful family protest in Washington.

By Mark Kelly. Cross-posted at The Foundry.