Due to sensible points made in the comments, I have reworded and clarifed my question.
I am trying to setup a world where due to reasons (mystical or alien) people have been going missing with no information over a period of time. They just seem to vanish without leaving any traces behind (no one sees them go missing). Eventually various governments/international agencies will pick up on these disappearances and conduct their investigations.
How many people would need to disappear in a year across the world for this to eventually be noticed (preferably after at least 1 year)?
**While I am aware that police would get involved with any missing persons case, i'm more curious about how many would need to go missing before its seen as unnatural and possible measures would be taken by countries worldwide (im specifically looking for governments changing polices or separately investigating this not just journalists reporting it or social media outcries)