30 missing person reports made to PSNI every day
Vast majority are found within 72 hours, but some have been gone for years
Around 30 people are reported missing to the PSNI every day in Northern Ireland.
A total of 43,235 cases were recorded from January 2015 to November 2018, figures show.
The vast majority turned up safe within a matter of days.
Of the total number of cases, 98% (42,438 people) were located within 72 hours, and of those 94% (40,740) were found within 24 hours.
However, as the PSNI must respond to every report of a missing person, it has led to concerns about the increased pressure on police resources.
The figures were revealed after a Freedom of Information request to the PSNI.
A breakdown of the data shows that over the near-four-year period, 25,039 of missing people were male, 18,106 were female and 88 were transgender.
The highest number of those reported missing were aged between 10 and 19.
In 2015 this age group accounted for 6,018 of missing persons cases, in 2016 it was 6,777 people, and in 2017 a total of 6,266. In 2018 there were 4,708 cases in this age group.
Meanwhile more than 700 children aged nine and under went missing over the past four years, with 763 cases reported to the PSNI.
Of those, 746 were found within 72 hours and 730 within 24 hours.
Furthermore, 52 people aged 90 to 100 went missing, all of whom were located within 24 hours.
In recent years the PSNI has been using social media to post appeals for missing people, and these usually get a huge response, which may explain why so many are quickly traced.
SDLP MLA Nichola Mallon said from her experience in her north Belfast constituency, she believes a lack of services to combat mental health and addiction is contributing to a high number of missing persons.
She said: "We would know that police officers spend a considerable amount of time trying to find someone who is missing from A&E with mental health conditions or who are reported missing by their families because they are so concerned about their fragile state and their welfare.
"When the police are searching for missing persons, that means they aren't able to do different things like attend to other police incidents, like burglaries, and it is stretching police resources.
"This is one of the many reasons why we need to have much more support services, treatments, including in-bed patient facilities for children and young people and adults battling with mental health and addiction issues.
"If we did have much more when it comes to treatment services and support for people struggling with mental health and addiction, I don't think we would see such high numbers."
UUP MLA Alan Chambers, who sits on the Northern Ireland Policing Board, said he would be raising the issue at its next meeting, to seek comparisons with other police forces.
He added: "I'm hoping it's not just uniquely a Northern Ireland problem."
Mr Chambers said the figure pointed towards the "pressures on the health service" and also acknowledged the daily pressures on the PSNI.
"The police sign up to preserve life and property and that's what the police do. Thankfully we have the police there to do that job and I know they have an awful lot of other competing pressures on them, and they have an awful lot of pressures put on them that are put on them needlessly sometimes.
"But when somebody goes missing - and so many people go missing - sometimes they do end up with a tragic outcome and I'm sure the police don't begrudge the amount of time they have to spend on trying to find people who are missing. But it is one of the roles of the police."
Mr Chambers praised the role of social media, which provides the PSNI with a platform to share an image of a missing person that can be viewed around the region instantly.
He added: "People have a lot of criticism of social media, but I think that this is one area where social media can come to the fore and can be a really useful tool to the community."
In a small number of cases, however, people have been missing for many years.
The PSNI website lists cases of long-term missing people. In some instances the cases have since become murder enquiries.
Among the people who have been missing for the longest is Timothy Hall who disappeared in February, 1983.
Another, Alexander Carson, vanished in January 1990.
Cookstown man Gerard Conway disappeared in February 2007 and Mark Gourley was last seen in March 2009.
Superintendent McMillan said the PSNI receives reports of missing people on a daily basis, adding: "Those reports can be made by family, friends, associates, carers or other agencies with statutory responsibilities for example.
"The circumstances that contribute to a person being reported as missing are often complex and could be a combination of, or linked to, reasons of health, personal trauma, instability in their environment, relationship changes, personal decisions or perhaps for other reasons unknown.
"The personal circumstances of each individual who has been reported missing vary and can be unique to that person. For some, being missing may be out of character, whereas others may have been reported missing before."
Supt McMillan said all cases are assessed by officers, adding: "Police therefore treat all missing people reports on an individual case by case basis and an early assessment takes place to identify and mitigate risk and harm, and to appropriately prioritise actions to locate that person as safely and quickly as possible.
"Police are continuing to work with statutory partners and other groups in an effort to ensure that the collective societal support for those who are vulnerable is cohesive and consistent and contributes to prevention and care.
"Once a person is reported missing, police will reach out to whomever can be identified who may be able to help locate that person, or share information that could contribute to their safe return. When necessary, and if deemed appropriate, social media is used to reach out to a larger group of people in an effort to locate a missing person and establish that they are safe and well."