Monthly variation appears to be a well established effect in the EPL and it's most noticeable in the amount fouls committed per game.The number rises slightly after the first month of the season before showing a general downward trend for the rest of the campaign.There are occasional upward blips,most notably in December,possibly as a result of larger festive crowds.The most interesting question regarding foul counts is whether after an initial rise in number the teams self regulate and become more restrained or whether the competitiveness of the tackling remains broadly consistent and it is the officiating that varies. In tournament soccer referees do tend to be excesively harsh in their interpretation of what is a foul in the earlier exchanges before relaxing their stance as the competition progresses.
The reduction in fouls late in the season is possibly easier to understand.Players are either looking forward to the beach or important international tournaments.There will be games that have a huge bearing on relegation or the title,but these type of games will be outnumbered by other less vital matchups.A large downward spike in the number of red cards coupled with a decrease in fouls and increase in shots in April indicates the games becoming more benign later in the season.
Correlated varibles unsurprisingly tend to follow each other step by step.Goals peak relatively early in the season,level off mid year before peaking again towards the end of the campaign. Shots,shots on target and corners generally follow the trend set by goals.
The really interesting question is why the monthly variation happens.Is it down to coaching tendencies,is some of it driven by the officials or is it weather related?