We aggregated the count of sightings per year based on the dimension of shape of the UFO object described. We grouped shapes like line, light, flash etc as One Dimensional shapes. Shapes like ball, round as Two Dimensional shapes. Likewise any object description or shapes like sphere, cylinder as Three Dimensional shapes. This visualization shows that one Dimensional shapes were reported at the maximum.
Please note the data covered is only 38 percent of the whole data (~65000 rows).