Since Niantic released Pokemon Go Gen 2 patch, there are lots of additions to the game, particularly on the evolution system. As reported previously, the new Pokemon update will bring five new evolution items similar to previous Pokemon games. These evolution items are known as Sun Stone, Metal Coat, Dragon Scale, King's Rock and Up-Grade. All of them can be looted from various PokeStops. However, several players are wondering on how often these special evolution items drops.
According to Otakukart, trainers first noticed that there is a fair chance to acquire an Evolution item on their seventh day spin streak. However, it seems like these items are getting harder to obtain after the discovery was revealed publicly.
Meanwhile, the data for these items including a rough estimate of the drop rates had already been found. Apparently, there are lots of theories regarding how the implementation of these Evolution items into the loot pool of PokeStops.
To make it simple, one theory that makes the most sense by far is that the Evolution items have a world drop. It means that the item does not have a chance of dropping from 1 out of 100 single player spin. However, the chance of dropping these Evolution items is from 1 out of 100 all player's spin.
For instance, someone installed a Lure Module on one PokeStops that attracted ten players. During the whole duration of the lure, it will total 12 spins from a single player. Overall, it will total 120 spins for the ten players present during that time. If the drop rate of the Evolution items is 1 out of 100, the chance of each players getting one would be around 10 percent.
On the other hand, at least one of them should receive an Evolution item if these items were on a world spawn timer. Furthermore, the odds of getting an evolution item for a single player are still the same. However, the chances of at least one of them collecting one will increase with more players spinning a particular PokeStop.