Photos circulating online claim to compare the crowd size at former president Barack Obama's 2009 inauguration and Donald Trump's inauguration Friday.
Side by side photos show a significant difference in the amount of people that attended the events each year. The comparison shows a packed space at the National Mall for the 2009 inauguration and a sparse crowd for this year's inauguration.
According to the Associated Press, both photos were taken shortly before noon from the top of the Washington Monument.
Estimates ahead of Friday's inauguration, expected anywhere from 700,000 to 900,000 people -- about half the amount that turned out for Obama's first inauguration -- to attend the inauguration of the 45th president.
But final counts of attendees still aren't in. Official photos from Getty and the Associated Press of the inauguration of Donald Trump Friday afternoon showed a crowded National Mall during at the time he was officially sworn in.
According to Washington's Metro system, 193,000 trips were taken as of 11 a.m. on Inauguration Day this year. The transit system said there were 513,000 trips taken on the day in 2009.
The swearing-in ceremony began around 11 a.m.
This year and in 2009, thousands of people were delayed from entering the National Mall. This year, Trump supporters were slowed down by protesters. In 2009, Obama supporters were delayed due to "logistical hold-ups at security checkpoints," the AP reported.
Charles Seife, a mathematician and professor of journalism at New York University, said estimating crowds is difficult.
"The best way is by aerial photography ... Take pictures and count heads, but even that is fraught," Seife said, according to Vox. "Pictures are taken at particular times, and (crowd) density may change over time. You're not going to see everybody. People will be popping in and out of buildings. There are people under trees. You can get a pretty sizable estimate, but it's not perfectly accurate."
And even then, he said, estimates can be skewed.
"Almost everyone who has tried to make a crowd estimate has a vested interest in what the outcome of the estimate is," Seife said in a in 2011 interview. "Whenever you see a crowd estimate, you have to wonder where it's coming from."
For now, it's unclear just how many people attended the historic event this year.