I just didn't know people actually tried to quantify the home field advantage over officiating:

The roar of the crowd may subconsciously influence some referees to give an advantage to the home team, according to a study that examines the results of over 5,000 soccer matches in the English Premier League. The matches were played between 1992 and 2006, and involved 50 different referees, each of whom had officiated at least 25 games within that time period.

...Boyko studied the number of goals scored by a team at home versus those scored while away, and found that teams scored 1.5 home goals on average, and 1.1 while away. Crowd size also had an impact on the number of goals scored by the home team, and for every additional 10,000 people in the crowd, the advantage for the home team increased by about 0.1 goals.