"For equally matched boxers (‘‘relative quality’’ = 0), expected probability of a home win was 0.57 for knockouts, 0.66 for technical knockouts and 0.74 for points decisions. The results of the present study lend generalsupport to the notion that home advantage is more prevalent in sports that involve subjective decision-making." http://wlv.openrepository.com/wlv/bitstream/2436/7759/1/Nevill9.pdf Haven't read that in detail, but it seems there is favouritism in judging decisions. I guess a mixture of crowd reactions, subconscious pressure to favour the favourite and foul play all factor.
In my limited experience of around 20fights when you fight at home it can be adavantageous as when you land a punch or two the roar of the crowd encouraging you motivates you to follow it up and keep throwing punches, it gives you more energy. When you fight away you can land what you think are good punches but there is no response from the crowd and you start to doubt whether t was a decent punch or not. You also feel under more pressure when you're caught by the home fighter and the crowd roars him on.It all impacts on what you're thinking and your motivation. I used to prefer fighting away from home though as there is no pressure of fearing that you might let down your family or friends. Now I'd rather fight at home.