Regarding My Ping

My original ping is 20, 19. The problem i have noticed is that it stays 20,19 for 2 weeks then it suddenly jumps up to 30 for like a month then comes back down. I'm just interested to know if that is from your side (servers) or my side (broadband) that causes that too happen, its unlikely that my broadband would cause it becuase i do have a good package with them so i wanted to know. I know its not much difference but it just bother me why my ping does that, so any solution or reason would be appreciated thank you.