So how exactly can you lose 150,000 people? For perspective, that's a number twice the size of the crowd that will fill Qualcomm Stadium for Super Bowl XXXVII today.
It's unclear how, but San Francisco police managed to lose that many last weekend when judging the turnout at the anti-war march and rally.
The police first said 40,000 people took part in the protest. Later they upped it to 55,000. By Monday, they changed it to 100,000 to 125,000. Still later, a police spokesman said 150,000 was a "safe estimate" while acknowledging it could have been as high as 200,000.
Meanwhile, organizers of the event, International ANSWER -- which stands for Act Now to Stop War and End Racism -- all along stuck by their count of 200,000, with good reason.
Police eyeballed it, looking only at the number of people at Civic Center Plaza. ANSWER had volunteers posted at Seventh and McAllister streets counting the marchers. They tallied 1,000 people a minute for 170 minutes, and then added a "conservative" number of people who took side streets to get to the Civic Center.
Having worked as a reporter in San Francisco, I have much respect for the SFPD -- but estimating the size of crowds has never been its strength. They tend to underestimate crowds for protests and overestimate for parades.
Using a police guesstimate of a Chinese New Year's parade crowd one year, I calculated there would have to have been 5,000 on-lookers on every block, on each side of the street, the entire length of the parade -- an absurd embellishment.
Since Saturday, San Francisco police have acknowledged their crowd-gauging methods are inadequate -- and have pledged to improve them. But for the protesters themselves, the damage was done.
Most media recorded the size of the San Francisco protest -- one of a series across the nation -- as a range starting at 40,000. It's unlikely many carried the Police Department's corrections a day or two later.
Was this really so damaging?
In a word, yes. In missing the size of the protest, the public missed its significance. A demonstration of 40,000 is newsworthy. A protest of 150,000 to 200,000 is historic.
For all its history of activism, the city hasn't seen a protest of that size since Vietnam. Even then it was a rally to end a war. Saturday's demonstration was intended to stop one from starting.
More to the point, in misjudging the size of Saturday's protest, many -- including the Bush administration, the media and myself -- misjudged its makeup.
Yes, there were the jugglers, naked demonstrators and people dressed in body bags -- who tend to dominate the attention of television cameras. But there also were lawyers, teachers, health-care professionals, parents pushing strollers -- and senior citizens who had never before participated in a demonstration.
A similar protest in San Francisco on Oct. 26 drew an estimated 80,000 people.
So where did these 70,000 to 120,000 new people come from? The evidence suggests they came from the center, that place where the majority of Americans have been since Sept. 11.
Unlike many demonstrations held since 9/11, this wasn't a protest made up of the far left. The evidence indicates this was a protest of the left, of the center and, in growing numbers, of the right.
Recent polls support this migration away from conditional support for U.S. military action in Iraq. A Newsweek poll released a week ago found that 60 percent of Americans want the president to allow more time before seeking military action.
Three days later, a Washington Post-ABC News poll showed that seven in 10 Americans would prefer to give U.N. weapons inspectors months more to continue their search.
Meanwhile, the president's support continues to slip. Those who approve of how he is handling the Iraq situation is now about equal to those who disapprove. Just a month ago, the number was 58 percent approve to 37 percent disapprove.
The number of those who believe Bush has sufficient reason to go to war also has dropped. In September, the number was 48 percent. This month it was down to 39 percent.
So what has changed? Nothing. And that's the difference. In September, many of these people expected U.N. weapons inspectors to produce the evidence that Iraqi President Saddam Hussein's production of chemical, biological and nuclear weapons posed a significant threat to national security.
But so far, that hasn't happened. Still, the Bush administration refuses to give ground, to the detriment of relations with Germany, France and other allies. Just this past week, the president again signaled his willingness to go to war with Iraq -- with or without U.N. Security Council approval.
It's a position that a growing number of Americans are unwilling to support.
While San Francisco police lost sight of 150,000 people, they at least acknowledged their mistake. The White House, however, continues to pretend they don't exist.
The president might ignore a number, but he can't ignore a simple truth: on the issue of unilateral war with Iraq, these protesters, not he, now speak for the majority.