Ultimate Team is always a huge talking point throughout a year of a FIFA game, particularly towards the end of FIFA 16, we have seen a huge amount of discussion around the fitness glitch and the chemistry style glitch.
A thread/discussion we found on reddit by user u/OkejBerg, who is clearly an intelligent guy figured out that base chemistry is 4.9 (out of 10). He, along with various others in the FIFA community, ran a series of experiments based around a skill move that can only be performed by players who have a certain stat in dribbling.
Here is the formula that he ended up coming up with, to determine what base chem is:
(individual chem of player + 0.75) + ((team chemistry/10) x 0.25) = (base chemistry).
That might seem like a load of twoddle, to you. What it basically means, is that for your player to receive any boosts, from their chemistry style, they must have at least 5 chemistry to do so. If they have less than 5 chemistry, then they will suffer a reduction in stats.