It would be hard to tell. Many people do not share when they have had an experience like this. But Mexico City, Mexico has many sightings with literally hundreds of people seeing and filming strange lights and flying things on a pretty regular basis.
UFO sightings predate recorded history.
Officially, UFO reported sightings are not available until early in the new year. So 2011 sightings won't be published until 2012.
So many that the town of St. Paul, Alberta has built a UFO landing site.
I think it was 2007 with 15 reported sightings.
The year 2007 had 15 reported sightings.
There are many accounts of UFO sightings by military and commercial pilots including NASA astronaughts.
Mexico has over 100
So few sightings are actually reported, there are no reliable statistics available.
Below are a couple of sites with the most recent UFO reports.
at the Nevada desert
On average there are over 600 reported sightings of UFOs annually.
I believe there was a sighting in Jan. of 2012. Below is a link to the most recent UFO sightings.