By the numbers: Missing persons in the USA

Kevin Kepple, Marianne Epstein, Lori Grisham | USA Today Network

On average, 90,000 people are missing in the USA at any given time, according to Todd Matthews from the National Missing and Unidentified Persons System, or NamUs, a national database for missing people.

In light of the recent disappearance of Hannah Graham from Charlottesville, Va., USA TODAY Network looks at the numbers of missing people from the FBI's National Crime Information Center, NCIC. Unless otherwise noted, these data are accurate as of Sept. 1.

"The first 12-24 hours are the most critical in an active missing persons investigation," Amy Dobbs, an investigator with the Knox County Sheriff's Office, told USA TODAY Network. "The longer it takes for a case to be reported and become an active investigation, the less likely a positive outcome will occur."

For children, the first three hours are especially critical because 76% of abducted children who are killed die within that time frame, according to a 2006 study by the Washington State Attorney General's Office.

If someone you know is missing, call 911 and report it as quickly as possible, Dobbs said. There is no mandatory time period that you need to wait to file a missing persons report. You can also report the missing person to NamUs, which will verify the information with law enforcement and list it on the NamUs site.